Bulletin of the American Physical Society
2013 Joint Meeting of the APS Division of Atomic, Molecular & Optical Physics and the CAP Division of Atomic, Molecular & Optical Physics, Canada
Volume 58, Number 6
Monday–Friday, June 3–7, 2013; Quebec City, Canada
Session Q1: Poster Session III (4:00 - 6:00PM) |
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Room: 400A |
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Q1.00001: FUNDAMENTAL SYSTEMS AND PRECISION MEASUREMENTS III |
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Q1.00002: Blackbody radiation shift in the Sr optical atomic clock Sergey Porsev, Marianna Safronova, Ul'yana Safronova, Mikhail Kozlov, Charles Clark We evaluated the static and dynamic polarizabilities of the $5s^2~^1\!S_0$ and $5s5p~^3\!P_0^o$ states of Sr using the high-precision relativistic configuration interaction + all-order method. Our calculation explains the discrepancy between the recent experimental $5s^2~^1\!S_0 - 5s5p~^3\!P_0^o$ dc Stark shift measurement $\Delta \alpha = 247.379(7)$ [Middelmann {\it et. al}, Phys. Rev. Lett. {\bf 109}, 263004 (2012)] and the earlier theoretical result of 261(4)~a.u. [Porsev and Derevianko, Phys. Rev. A {\bf 74}, 020502R (2006)]. Our present value of 247.5~a.u. is in excellent agreement with the experimental result. We also evaluated the dynamic correction to the BBR shift with 1\% uncertainty; -0.1492(16)~Hz. The dynamic correction to the BBR shift is unusually large in the case of Sr (7\%) and it enters significantly into the uncertainty budget of the Sr optical lattice clock. We suggest future experiments that could further reduce the present uncertainties. [Preview Abstract] |
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Q1.00003: Strontium clock comparisons and prospects at LNE-SYRTE Ulrich Eismann, Chunyan Shi, Mikhail Gurov, Rodolphe Le Targat, J\'er\^ome Lodewyck, Yann Le Coq, Jocelyne Gu\'ena, Michel Abgrall, Peter Rosenbusch, Giovani-Daniele Rovera, S\'ebastien Bize, Philippe Laurent Recently, the caesium fountain clocks currently defining the SI second have been superseded in both stability and accuracy by atomic clocks referenced to optical transitions. Here we present frequency comparisons between two similar state-of-the-art strontium optical lattice clocks. The clocks are in agreement within their accuracy budget with a total uncertainty of $1.6\times10^{-16}$. A reproducible link is established between the strontium clock frequency and the current definition of the SI second by consistent comparisons of these clocks with three of the best caesium fountains. The measured strontium clock frequency is $429\,228\,004\,229\,873.10$\,Hz, with a total uncertainty of $3.1\times10^{-16}$ henceforth limited by the accuracy of the microwave clocks. Furthermore, we will discuss the prospects for improving the accuracy and stability of strontium optical lattice clocks. Currently, the largest contribution to the error budget is the light shift related to black-body radiation from the vacuum vessel surrounding the trap. A new-generation vacuum vessel with a well controlled temperature will allow to bring the accuracy into the low $10^{-17}$ range. [Preview Abstract] |
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Q1.00004: Pushing the uncertainty of a ytterbium optical lattice clock towards $10^{-17}$ fractional frequency Nathan Hinkley, Jeff A. Sherman, Kyle Beloy, Nathaniel B. Phillips, Richard W. Fox, Chris W. Oates, Andrew D. Ludlow Ultracold alkaline-earth atoms confined in an optical lattice are well-suited as high-accuracy frequency standards. After a previous evaluation of systematic frequency shifts, our ytterbium optical lattice clock demonstrated $3.4\times10^{-16}$ fractional uncertainty. Here we summarize recent efforts which improve this uncertainty and the optical lattice clock overall, including precise characterization of the thermal radiation environment; dynamic blackbody radiation effects; and lattice-induced Stark shifts from the E1 polarizability, hyperpolarizability, and multipolar contributions. [Preview Abstract] |
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Q1.00005: Spectroscopy of the $^{199}$Hg Optical Clock Transition at 265.5 nm Christian Lytle, Justin Paul, R. Jason Jones Neutral Hg is an excellent candidate for a stable and accurate atomic clock. The doubly-forbidden clock transition at 265.5 nm can provide an extremely high-quality resonance factor (Q) when confined in an optical lattice at the Stark-shift free ``magic'' wavelength. A key feature of the Hg system is the expected reduced uncertainty of black-body radiation induced Stark shifts compared to other optically-based neutral atom clocks. We demonstrate precision spectroscopy of the $^{1}S_{0}$ - $^{3}P_{0}$ clock transition in $^{199}$Hg in a MOT. The MOT population of $10^6$ atoms was depleted by over 70\% using 3 mW from a cavity-stabilized probe laser tuned to the clock transition. We present our characterization of the transition and efforts to implement a stable Hg clock system. [Preview Abstract] |
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Q1.00006: Record Stability via Improved Laser Coherence in Strontium-87 Optical Clocks Sara Campbell, Travis Nicholson, Michael Martin, Benjamin Bloom, Jason Williams, Michael Bishof, Xibo Zhang, Matthew Swallows, Jun Ye Many-particle clocks are promising candidates for next-generation frequency standards because quantum projection noise scales down with the square root of atom number. Previously, these clocks had been unable to demonstrate stability better than that of single-particle clocks, due to laser noise-induced instability via the Dick effect. We show that a better optical local oscillator with a $10^{-16}$ thermal noise floor directly results in a tenfold improvement in clock stability, now reaching $1\times 10^{-17}$ in 1000 s [1]. Leveraging the superior precision of a many-particle clock, we are working toward a full systematic evaluation of our clock accuracy with a goal of $1\times 10^{-17}$ fractional uncertainty. One of the important systematics inherent in many-particle clocks is the density-dependent frequency shift. In a new system that traps thousands of atoms at low density, we now measure the density shift with a fractional uncertainty of $8.2\times 10^{-19}$ [1]. Additionally, to further improve our clock stability, we have developed a novel technique to evaluate the noise spectrum of our ultra-stable laser using $^{87}$Sr atoms as a quantum reference [2]. \\[4pt] [1] T.L. Nicholson, et al., PRL 109, 23081 (2012).\\[0pt] [2] M. Bishof et al., in preparation (2013). [Preview Abstract] |
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Q1.00007: Test of Lorentz Invariance at the Amundsen -- Scott South Pole Station Marc Smiciklas, Andrew Vernaza, Michael Romalis Tests of Lorentz and CPT symmetry provide one of the few ways to experimentally access Planck-scale physics. Currently the most sensitive Lorentz symmetry tests for fermions are performed with atomic spin co-magnetometers. Earth rotation represents a large background for such experiments due to gyroscopic spin interaction. To improve the limits on vector and tensor Lorentz-violating interactions we have installed a $^{21}$Ne-Rb co-magnetometer at the Amundsen -- Scott South Pole Station. The experiment is mounted on a precision air-bearing rotating platform aligned to the local vertical to eliminate most Earth-bound sources of systematic errors. We plan to collect data over the austral winter. We will describe the experience of operating the experiment at the South Pole and present the latest results. [Preview Abstract] |
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Q1.00008: Kinetic Energy and the Equivalence Principle Holger M\"uller, Michael Hohensee Constraints on violation of the Einstein equivalence principle (EEP) can be inferred from tests of the universality of free fall or atom interferometry. In generalized models describing EEP as a perturbation to known physics, such as the standard model extension, the combination of a particle-specific modification of the space-time metric, along with interactions with to a field that is non-metrically coupled to spacetime, makes it possible for the total observable EEP-violation to cancel in the motion of free protons, neutrons, and electrons, while manifesting in the motion of free antiparticles. We show that such hidden forms of EEP-violation can be ruled out using ordinary matter, as modified metric violation of EEP also couples to the internal kinetic energy of bound systems of particles. Using a Woods-Saxon potential to calculate the kinetic energies of nucleons bound within a wide range of atomic nuclei, we estimate the sensitivity of existing and planned tests of EEP to such hidden forms of EEP violation. We show that existing limits on EEP-violation, hidden or otherwise, are significantly better than previously thought, with important implications for future tests of EEP. [Preview Abstract] |
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Q1.00009: Search for violation of Lorentz symmetry and variation of the fine-structure constant with radio-frequency spectroscopy of atomic dysprosium Nathan Leefer, Michael Hohensee, Christian Weber, Dmitry Budker, Celal Harabati, Vladimir Dzuba, Victor Flambaum Atomic dysprosium (Dy) has been found to be a useful system to look for new physics beyond the Standard Model and General Relativity. Large relativistic corrections to electron energies, owing to the high nuclear charge ($Z = 66$), make the energies of atomic states in Dy highly sensitive to proposed variations of the fine-structure constant, $\alpha$. Due to the reduced screening of the nuclear charge, the relative energy of excited states in Dy are also sensitive to violations of Local Lorentz Invariance (LLI) and the Einstein Equivalence Principle (EEP) as parametrized by the Standard Model Extension. The existence of an electric-dipole transition between a pair of nearly-degenerate excited states in Dy allows us to place some of the best limits on these effects with relatively low precision radio-frequency spectroscopy. We present the details of our experiment used to constrain variation of $\alpha$ at the level of $|\dot{\alpha}/\alpha|<10^{-16}$ yr$^{-1}$. In the context of the Standard Model Extension we bound violation of LLI for electrons at the level of $10^{-17}$ for the $c_{\mu\nu}$ tensor that modifies the kinetic term in the electronic QED Lagrangian. [Preview Abstract] |
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Q1.00010: Lorentz symmetric n-particle systems without ``multiple times'' Felix T. Smith The need for multiple times in relativistic n-particle dynamics is a consequence of Minkowski's postulated symmetry between space and time coordinates in a space-time $s=[x_{1},..,x_{4}]=[x,y,z,ict]$, Eq. (1). Poincar\'e doubted the need for this space-time symmetry, believing Lorentz covariance could also prevail in some geometries with a three-dimensional position space and a quite different time coordinate. The Hubble expansion observed later justifies a specific geometry of this kind, a negatively curved position 3-space expanding with time at the Hubble rate $l_{H}(t)= l_{H,0}+c\Delta t$ (F. T. Smith, Ann. Fond. L. de Broglie, 30, 179 (2005) and 35, 395 (2010)). Its position 4-vector is not $s$ but $q=[x_{1},..,x_{4}]=[x,y,z,il_{H}(t)]$, and shows no 4-space symmetry. What is observed is always a difference 4-vector $\Delta q = [\Delta x, \Delta y, \Delta z,ic\Delta t]$, and this displays the structure of Eq. (1) perfectly. Thus we find the standard 4-vector of special relativity in a geometry that does not require a Minkowski space-time at all, but a quite different geometry with a expanding 3-space symmetry and an independent time. The same Lorentz symmetry with but a single time extends to 2 and n-body systems. [Preview Abstract] |
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Q1.00011: QUANTUM INFORMATION PROCESSING |
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Q1.00012: A scalable monolithic ion trap in three-dimensional geometry Ye Wang, Kihwan Kim We develop a three-dimensional monolithic ion trap that will have a deep trap potential and can be extended to contain multiple zones similar to two-dimensional surface traps. The trap will be fabricated by gold coating on a laser-machined alumina plate which has been successfully used for trapping ions. The basic structure of the trap is analogous to the combination of the three-layer trap [1] and the symmetric trap [2], but the post-processing assembly of multi-layers is not required. On a single layer of alumina plate, we implement RF electrode and twenty DC electrodes. Our trap is expected to demonstrate high radial trap frequency and is able to produce a uniformly spaced ion chain. Furthermore, the technology can be extended to implement a junction structure on the trap to transport ions for connecting different trap zones. This work was supported by the National Basic Research Program of China Grant 11CBA00300, 2011CBA00301, 2011CBA00302, the National Natural Science Foundation of China Grant 61073174, 61033001, 61061130540. KK acknowledges the support from the Thousand Young Talents program.\\[4pt] [1] W. K. Hensinger, et al., Appl. Phys. Lett. 88, 034101 (2006).\\[0pt] [2] F. Shaikh, et al., arXiv:1105.4909. [Preview Abstract] |
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Q1.00013: Microwave-controlled qubit interactions in a cryogenic surface electrode ion trap Malte Niemann, Timko Dubielzig, Anna-Greta Paschke, Martina Carsjens, Matthias Kohnen, Christian Ospelkaus Multi-qubit interactions for quantum information processing with trapped ions require a coupling between individual ion-qubits and a shared motional degree of freedom. Recent experiments have shown how such interactions can be realized using microwave near-fields rather than laser fields. This holds great promise for integration, simplification and fidelities. One successful approach to create the required field configuration uses currents in three near-by microwave electrodes integrated on a chip [1,2]. Relative phase and amplitude stability of the currents may be one of the main limitations with this approach. We have designed an electrode configuration that requires only a single microwave electrode to create the field required to address sideband transitions. This technique requires close proximity of ion-qubits to conductors, where anomalous motional heating can be a source of decoherence [3]. To suppress these effects in our experiments, we have developed a low-vibration closed-cycle cryogenic setup. We will discuss this setup including the vacuum and imaging design as well as the proposed microwave electrode configuration.\\[4pt] [1] Ospelkaus et al., Nature 476, 181-184 (2011)\\[0pt] [2] Allcock et al., arXiv:1210.3272 [Preview Abstract] |
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Q1.00014: A hybrid trapped ion system with ultrafast pulse lasers Shuoming An, Mark Um, Dingshun Lv, Jing-Ning Zhang, Kihwan Kim, Lu-Ming Duan We report the experimental progress to realize a hybrid trapped ion system, where Barium and Ytterbium ions share vibrational modes in the same radio-frequency trap. The hybrid system is considered to be essential for the realization of a large scale quantum system with trapped ions. For the system with a few tens ions, continuous cooling of the whole ion chain is required during massive quantum operations. We can use the internal state of Ba ion for quantum computation and transitions of Yb for refrigeration of the system or vise versa. For the trapped ion based quantum repeater, a local entangling operation between different atomic ions is critical procedure to protect qubit information during enormous trials of probabilistic photon connection. We can realize the entangling operation between Ba and Yb ions by applying two pairs of picoseconds laser beams at the wavelengths of 355nm and 532nm, which are generated by frequency doubling and tripling of Nd:YAG laser. This work was supported by the National Basic Research Program of China Grant 2011CBA00300, 2011CBA00301, 2011CBA00302, the National Natural Science Foundation of China Grant 61073174, 61033001, 61061130540. KK acknowledges the support from the Thousand Young Talents Plan. [Preview Abstract] |
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Q1.00015: Surface-electrode ion traps and technologies for scalable quantum information processing S. Charles Doret, Jason M. Amini, Kenton R. Brown, Chris Shappert, David Landgren, Arkadas Ozakin, Harley Hayden, C.-S. Pai, Curtis E. Volin, Lisa M. Lust, Alexa W. Harter As experiments in quantum information processing with trapped ions progress from few to many ion-qubits, it is imperative that trap designs and technologies keep pace. Surface-electrode traps offer one path to scaling experiments to large numbers of ions, but they will require the integration of many trapping zones and associated interconnects. We have developed a new trap (``Satellite'') with separated loading, storage, and computation regions connected by a newly-designed X-junction. The storage regions feature inter-digitated control electrodes, allowing storage of up to twenty ions in each zone with only a moderate increase in the trap's lead count. Even so, future traps of increasing complexity will create challenges for experimental control. With this in mind, we are developing in-vacuum electronics~\footnote{In collaboration with Honeywell International} to reduce requirements for external control systems and simplify vacuum feedthrough requirements. We have also demonstrated co-trapping of $^{40}$Ca$^{+}$ / $^{171}$Yb$^{+}$ and are exploring strategies, both theoretically and experimentally, for sympathetic cooling of dual-species ion chains. [Preview Abstract] |
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Q1.00016: Trapping Ions in a 2-pi Parabolic Mirror Chen-Kuan Chou, Gang Shu, Thomas Noel, John Wright, Richard Graham, Boris Blinov Single trapped ion qubit is an excellent candidate for quantum computation and information due to its low decoherence, ease of control and detection, and ability to couple to a photon, the flying qubit. Efficient coupling between ions and resonant photons is crucial for ion-photon and remote-ion entanglement protocols. We describe the operation of a RF ion trap in which a reflective parabolic surface serves as of the trap's electrodes. This parabolic mirror covers a solid angle of approximately 2 pi around the trapped ion, and allows precise ion placement at the focal point of the parabola. We measured approximately 39{\%} fluorescence collection from a single ion with this mirror. With the advantage of producing a collimated photon beam, we expect to couple the ion fluorescence into a single-mode fiber in a straightforward way. [Preview Abstract] |
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Q1.00017: Microwave quantum logic spectroscopy and control of molecular ions Molu Shi, Peter Herskind, Isaac Chuang A general method for rotational microwave spectroscopy and control of polar molecular ions is considered, which combines several techniques developed for quantum information processing with both neutral atoms and atomic ions. Our method makes use of spatially varying AC Stark shifts, induced by far off-resonant, focused laser beams to achieve an effective coupling between the rotational state of a molecular ion and the electronic state of an atomic ion. In this setting, the atomic ion is used for read-out of the molecular ion state, in a manner analogous to quantum logic spectroscopy based on Raman transitions. Key to this approach is that it is compatible with the use of microwave fields in the spectroscopy, which avoids the need for technically challenging Raman lasers. In addition to high-precision spectroscopy, the techniques outlined here allow for rotational ground state cooling, and form the basis for quantum information processing with polar molecular ions. All elements of our proposal can be realized with currently available technology. [Preview Abstract] |
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Q1.00018: ABSTRACT WITHDRAWN |
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Q1.00019: Towards Quantum Simulations Using a Chip Ion Trap Chenglin Cao, Ken Wright, Daniel Brennan, Geoffrey Ji, Christopher Monroe We report our current experimental progress towards using chip ion traps for quantum simulation. Current progress is being made using a micro-fabricated symmetric trap from GTRI. This trap implements a novel two level design that combines the benefits of both surface traps and linear four-rod traps. The trap has 50 electrodes which allow for the fine control of the DC potential needed to create large anharmonic potentials, to join and split ion chains and to shuttle ions along the trapping axis similar to many surface traps. However this trap also has a much deeper trapping depth than conventional surface traps and improved optical access via an angled slot through the chip wide enough to accommodate higher power laser light which could cause surface charging or damage in a traditional chip trap. These advantages should allow trapping of long ion chains. We hope to use these features as the next step in increasing the size of current quantum simulations being done at Univ of Maryland, which are aimed at exploring quantum phenomena in spin systems in a regime inaccessible to classical simulation. This work is supported by grants from the U.S. Army Research Office with funding from the DARPA OLE program, IARPA, and the MURI program; and the NSF Physics Frontier Center at JQI. [Preview Abstract] |
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Q1.00020: Enabling Technologies for Scalable Trapped Ion Quantum Computing Stephen Crain, Daniel Gaultney, Emily Mount, Caleb Knoernschild, Soyoung Baek, Peter Maunz, Jungsang Kim Scalability is one of the main challenges of trapped ion based quantum computation, mainly limited by the lack of enabling technologies needed to trap, manipulate and process the increasing number of qubits. Microelectromechanical systems (MEMS) technology allows one to design movable micromirrors to focus laser beams on individual ions in a chain and steer the focal point in two dimensions. Our current MEMS system is designed to steer 355 nm pulsed laser beams to carry out logic gates on a chain of Yb ions with a waist of 1.5 $\mu $m across a 20 $\mu $m range. In order to read the state of the qubit chain we developed a 32-channel PMT with a custom read-out circuit operating near the thermal noise limit of the readout amplifier which increases state detection fidelity. We also developed a set of digital to analog converters (DACs) used to supply analog DC voltages to the electrodes of an ion trap. We designed asynchronous DACs to avoid added noise injection at the update rate commonly found in synchronous DACs. Effective noise filtering is expected to reduce the heating rate of a surface trap, thus improving multi-qubit logic gate fidelities. Our DAC system features 96 channels and an integrated FPGA that allows the system to be controlled in real time. [Preview Abstract] |
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Q1.00021: Quantum Information Processing Primitives in a Microfabricated Surface Ion Trap Emily Mount, So-Young Baek, Daniel Gaultney, Stephen Crain, Rachel Noek, Peter Maunz, Jungsang Kim Microfabricated surface ion traps provide a scalable option for building a trapped ion quantum information processor. These multi-segmented traps are fabricated using existing silicon processing technology and can provide the necessary electric fields to store a chain of ions and shuttle ions within the trap structure. Using a microfabricated surface trap made by Sandia National Laboratories [1] we trap individual $^{171}$Yb$^+$ ions and demonstrate fundamental quantum information processing primitives. Trap lifetimes of over 10 hours with cooling and 20 minutes without have been observed. High fidelity single qubit rotations of the hyperfine clock state qubit have been performed using a resonant microwave field. A single $\pi$/2 gate fidelity of 99.95\% has been observed using a randomized benchmarking scheme. Single qubit rotations using Raman transitions were realized, driven by a repetition-rate stabilized frequency comb. The addressing of ion motion using frequency combs has allowed for cooling the ion from the Doppler level (\={n} = 8 quanta) to less than one average quanta (\={n} = 0.8 quanta). Heating rates as low as 0.8 quanta/ms have been observed in this trap making it a good platform for motional gates.\\[4pt] [1] D Stick, et al., arXiv:1008.0990v2, 2010. [Preview Abstract] |
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Q1.00022: Coupling of ions to superconducting circuits Soenke Moeller, Nikos Daniilidis, Hartmut Haeffner We present experimental progress towards coupling the motion of ion strings to the resonant mode of a superconducting high-quality tank circuit. We consider such a coupling as the first step towards interfacing trapped ions with superconducting qubits. In our demonstration experiment, we aim to reduce the temperature of the resonant mode of the tank circuit by extracting energy from the circuit via laser cooling an ion string. One of the main experimental challenges is to construct a tank circuit with such a high quality factor Q that the ion-resonator coupling exceeds the environment-resonator coupling. Currently, we achieve Q = $60\;000$ at a frequency of $\omega=2\pi\cdot5.7\;\rm{MHz}$. For this mode, the coupling time-scale to the environment is on the order of 50~Hz. We plan to use a trap with an ion-electrode distance on the order of $100\;\rm{\mu m}$ resulting in an ion-resonator coupling of 1$\; $kHz. This coupling should reduce the electronic temperature of the resonant mode by a factor of 80 below the ambient temperature. For our trap geometry we expect a minimum trap depth of $50\; \rm{meV}$ for a trap drive frequency of $52\;\rm{MHz}$ with a $200\;\rm{V}$ amplitude. This results radial trap frequencies of $5.7\;\rm{MHz}$. [Preview Abstract] |
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Q1.00023: Thermodynamics and Quantum Correlations in Trapped Ion Crystals Thaned Pruttivarasin, Michael Ramm, Manuel Gessner, Hartmut Haeffner Crystals of trapped ions exhibit a broad variety of physical phenomena ranging from fundamental quantum effects with applications for quantum information theory to mesoscopic physics at the border to the classical regime. In our current experiments we are investigating the melting dynamics of larger ion crystals and the distribution and transport of energy in such systems. In another experiment in the quantum regime, we are aiming at detecting the signatures of nonclassical system-environment correlations in the dynamics of an open quantum system. We present a theoretical scheme which does not require control over the environment and that can be carried out by local operations on the open system only. [Preview Abstract] |
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Q1.00024: Progress towards loophole-free tests of the Bell inequalities by distributing ion-photon entanglement over long distances Le Luo, Chuanfeng Li, Yongjian Han, Yunfeng Huang We are developing a long term program to implement loophole-free tests of the Bell inequalities by generating entangled ion-photon pairs over long distances. Time-like interval and high detection efficiency are two essential components for a loophole-free test of the Bell inequalities. In our scheme, a pair of entangled photons (local and remote photon) from narrow-band spontaneous parametric down conversion (SPDC) will be used to produce time-like interval through a telecom fiber linking two cities separated by a distance of over 100 km in Anhui, China. Then an upconversion quantum interface will coherently transfer the qubit stored in the local SPDC photon to another photon at 370 nm which coincides the spontaneous emitted photon from trapped Yb ions. We will then implement a herald entanglement scheme by a joint measurement of both the upconversion photon and the spontaneous emitted photon which is entangled with a trapped Yb ion. Thus ion-photon entanglement can be generated between the remote SPDC photon and the trapped ion. Assuming perfect detection efficiency of the ion, a minimum detection efficiency 0.50 of the SPDC photon is required to close the detection loophole. We will present an analysis of this experimental scheme and report the current experimental progress. [Preview Abstract] |
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Q1.00025: ATOM OPTICS |
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Q1.00026: Slow atom scattering from magnetic media Timothy Roach, Katelyn Candee, Kevin Moran, Craig Richardson The use of magnetic field gradients to manipulate atomic motion has a long history, using a variety of field sources: permanent- and electro-magnet, time- and space-dependent, on macro- and micro-scopic scales. We use a curved sub-micron patterned permanent magnet made from recording media to scatter slow atoms arriving at near normal incidence. The atomic waves are expected to be both diffracted and focused. A cloud of Rb atoms from a MOT is released to fall $\sim$10cm to the magnetic surface and the atoms are probed with laser light after the interaction. Preliminary measurements of the scattered atoms will be presented. [Preview Abstract] |
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Q1.00027: Quantum superposition of massive molecules and molecular clusters in the time-domain Philipp Haslinger, Nadine Doerre, Jonas Rodewald, Philipp Geyer, Stefan Nimmrichter, Klaus Hornberger, Markus Arndt Recent experimental advances have allowed us to devise new molecular sources, interferometer arrangements and detection methods that open the path to testing and exploiting the quantum superposition principle, both using a range of different massive particles and with high sensitivity. Our most recent interferometer uses pulsed optical gratings [1]. This allows us to conduct experiments in the time-domain which eliminates most of all causes of velocity-dependent dephasing [2]. The gratings are realized by standing light waves of three nanosecond laser beams at $\lambda = $ 157 nm. This wavelength is short enough to achieve efficient single-photon ionization of a broad range of atoms, molecules and nanoparticles. In combination with an external electric field these pulses act dominantly as absorptive gratings in the time-domain. On the applied side the $O$ptical \textit{TI}me-domain \textit{MA}tter (OTIMA) interferometer can be used as a nanoruler for high-precision measurements of external forces or internal particle properties [3], too.\\[4pt] [1] Haslinger P., et al., \textit{Nature Physics}, accepted (2013), Reiger E., Opt. Comm. 264 326-32 (2006)\\[0pt] [2] Nimmrichter S., et al., \textit{Phys. Rev. A} 78, 063607 (2008)\\[0pt] [3] Berninger M., et al., \textit{Phys. Rev. A}, \textbf{76}, 013607 (2007) [Preview Abstract] |
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Q1.00028: Boosting the Sensitivity of Matter-wave Interferometers with Nonlinearity Kunal Das, Brian Kilpatrick, Tomas Opatrny, Michal Kolar We propose a mechanism to use nonlinearity arising from inter-particle interactions to significantly enhance rotation sensitivity of matter-wave interferometers. The method relies on modifying Sagnac interferometers by introducing a weak circular lattice potential that couples modes with opposite orbital angular momenta (OAM). The primary observable comprises of the modal population distributions measured at specific times. This provides an alternate mechanism for rotation sensing even in the linear non-interacting regime, while nonlinearity can improve the sensitivity, as well as operation timescales, by several orders of magnitude. We also present analogous results for a linear geometry with implications for force sensing. [Preview Abstract] |
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Q1.00029: What is the right time for path integrals? Eric Jones, Roger Bach, Herman Batelaan The Feynman path integral formulation of quantum mechanics has proven to be a powerful tool for calculations in matter optics. It is natural to introduce the path integral in the context of Young's double slit experiment for matter waves as Feynman did,\footnote{R. P. Feynman, Rev. Mod. Phys. \textbf{20}, 367-387 (1948).} perhaps after discussing the analogous situation for optics. While intuitive, this approach can lead to a \textit{pedagogical} misrepresentation of the theory, namely in the phase accumulated along single free-particle trajectories. How is the use of the accumulated phase, $2\pi L/\lambda_{dB} $, along a path of length $L$ justified? The free-particle action gives a phase that differs by a factor of two. The guiding principle that interference occurs only for two paths that are indistinguishable from one another provides a correct solution: interfering paths must originate and terminate at equal times. We will present several simple thought experiments to illustrate incorrect and correct methods for determining phase shifts. [Preview Abstract] |
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Q1.00030: Molecular matter waves -- tools and applications Thomas Juffmann, Michele Sclafani, Christian Knobloch, Ori Cheshnovsky, Markus Arndt Fluorescence microscopy allows us to visualize the gradual emergence of a deterministic far-field matter-wave diffraction pattern from stochastically arriving single molecules [1]. We create a slow beam of phthalocyanine molecules via laser desorption from a glass window. The small source size provides the transverse coherence required to observe an interference pattern in the far-field behind an ultra-thin nanomachined grating. There the molecules are deposited onto a quartz window and can be imaged in situ and in real time with single molecule sensitivity. This new setup not only allows for a textbook demonstration of quantum interference, but also enables quantitative explorations of the van der Waals interaction between molecules and material gratings.\\[4pt] [1] Juffmann et al., Nature Nanotechnolgy, 7, 297-300, (2012). [Preview Abstract] |
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Q1.00031: Experiments with a Single Bright Matter-Wave Soliton Incident on a Barrier David Tam, Paul Dyke, Jason Nguyen, Randall Hulet The defining property of a soliton is the stability of its shape which arises due to nonlinear self-focusing. We collapse a quasi-1D BEC of $^{7}$Li into a matter-wave soliton containing ${\sim} 60{,}000$ atoms. The collapse is controlled by adiabatically ramping the single-particle scattering length from a large and positive value to slightly negative using the broad magnetic Feshbach resonance in the $| F=1, m_F=1 \rangle$ hyperfine sublevel near 737 G.\footnote{Strecker, K. E., Partridge, G. B., Truscott, A. G. \& Hulet, R. G. Formation and propagation of matter-wave soliton trains. Nature 417, 150-153 (2002).} Dipole oscillations in a weakly harmonic 1D potential are initiated by pulsing on a magnetic field gradient, enabling us to observe the soliton's motion over several oscillation periods. We investigate dynamic interactions of the soliton with a single attractive or repulsive optical defect created by a narrow light sheet at the trap center. A repulsive defect can split a single soliton into two, and on the subsequent interaction at the defect, may enable coherent recombination, thus realizing a matter-wave interferometer. [Preview Abstract] |
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Q1.00032: Rotating sensing with an atom analog of the SQUID Changhyun Ryu, Malcolm Boshier After the SQUID was created to study and utilize quantum interference of currents flowing through Josephson Junctions connected in loop, it was developed into the most sensitive magnetometer known. An atom analog of the SQUID (an ``Atom SQUID'') would be sensitive, instead, to rotation. The study of the Atom SQUID is important given the need to develop compact and sensitive rotation sensors and the possibility of using it to study macroscopic quantum phenomena with a BEC. In previous experiments, we demonstrated Josephson Junctions (JJs) for an Atom SQUID with a ``Painted Potential'' method for manipulating a BEC. The critical current was measured by moving the JJs through a BEC to create a bias current. Compression of atoms was observed when the bias current exceeded the critical current, showing Josephson effects directly. In a rotating Atom SQUID the critical current is a periodic function of external rotation rate, with period $\Omega_0 = \hbar/m R^2$ for atoms of mass $m$ in a torus of radius $R$. In this poster we will describe progress toward measuring this modulation of the critical current, which will show the interference of currents flowing through Josephson Junctions and also serve as a proof of principle demonstration of rotation sensing with an Atom SQUID. [Preview Abstract] |
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Q1.00033: Progress on and Instrumentation for an Ion Inteferometer Jarom Jackson, James Archibald, Erickson Christopher, Dallin Durfee We describe progress on a cold ion matter-wave interferometer. The ions are generated by laser-cooling strontium and then photo-ionizing the atoms with a two-photon transition to an auto- ionizing state in the continuum. A pair of electrodes will set the kinetic energy of the ions. Splitting and recombining the quantum waves will be achieved using Raman transitions driven by a pair of laser beams. These beams are created by injection locking a pair of diode lasers with two beams from a master laser which have been shifted to differ in frequency by the strontium ion hyperfine splitting. Optical pumping and detection of the ions will be done with a laser locked to a column of strontium vapor which has been photo-ionized. [Preview Abstract] |
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Q1.00034: Achieving long interaction times with a free-oscillation atom interferometer A.J. Fallon, R.H. Leonard, R.A. Horne, T. Arpornthip, C.A. Sackett In a free oscillation interferometer, a trapped Bose-Einstein condensate is split into two packets using Bragg scattering from an off-resonant standing wave. The moving packets complete a full oscillation in the harmonic trap potential and are then recombined using another Bragg pulse. The resulting motional state is determined the interferometric phase between the packets. Free oscillation interferometers have been used to obtain measurement times as long as one second, and offer the potential to improve precision measurements of inertial and atomic phenomena. However, at long interaction times the interferometer is subject to a variety of technical effects, including vibrational noise, trap anharmonicity, phase curvature, phase diffusion, and fluctuations in the initial BEC state. We have developed a variety of techniques to understand and control these effects, including anharmonicity compensation, a reciprocating dual interferometer, passive and active vibration stabilization, and numerical and analytical analysis of the three-dimensional Gross-Pitaevskii equation. Results of these investigations will be described and current performance of the interferometer will be discussed. [Preview Abstract] |
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Q1.00035: Yb Bose-Einstein condensate Interferometer for h/m and $\alpha$ Ben Plotkin-Swing, Alan Jamison, Will Dowd, Anders Hanson, Alexander Khramov, Richard Roy, Subhadeep Gupta We report high-precision results from a matter-wave interferometer using a Yb Bose-Einstein condensate (BEC) as a source. This contrast interferometer measures h/m, where h is Planck's constant and m is the mass of an ytterbium atom, which is used to determine the fine structure constant $\alpha$. We will present the techniques and results from our current apparatus, including the highest accuracy measurement to date using a BEC matter-wave interferometer and our progress toward measuring and controlling the effects of atomic interactions. We will also describe a new apparatus, currently under construction, which is designed to yield a sub-part-per-billion measurement of $\alpha$. [Preview Abstract] |
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Q1.00036: Atom Interferometry in an Optical Cavity and Applications Justin Brown, Brian Estey, Paul Hamilton, Holger M\"uller Light pulse atom interferometers use pulses of light to coherently split matter waves and utilize interference to measure the relative phase between paths. Measurement sensitivity increases with the enclosed space-time area. Several techniques have been developed to increase momentum transfer including high order Bragg diffraction. This has been limited to 24 $\hbar k$ in a single pulse by laser power and beam quality such as wavefront distortions. We are developing an interferometer in a vertically-mounted 40 cm long Fabry-Perot cavity using cold Cs atoms. The cavity enhances available laser power, controls optical wavefronts, and is expected to provide $>100~\hbar k$ momentum transfer in a single Bragg diffraction process. Such a demonstration would provide a competitive gravimeter in a compact device. In addition, the optical cavity reduces uncertainties in beam alignment and divergence. This feature allows light pulses to enclose a well-defined spatial area for a Sagnac gyroscope with high scale factor stability. Finally, the compact design and large momentum transfer expected allow for the introduction of two source masses for a possible demonstration of the gravitostatic Aharonov-Bohm effect. We report on our experimental progress and discuss these applications. [Preview Abstract] |
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Q1.00037: A clock referenced to the rest mass of a single particle Chenghui Yu, Shau-Yu Lan, Pei-Chen Kuan, Brian Estey, Damon English, Justin M. Brown, Michael A. Hohensee, Holger M\"uller We demonstrate the operation of a Compton clock, one whose frequency is referenced to the mass of a single particle. Though it is well known that the wave function of a massive particle accumulates phase at the Compton frequency $\omega_{0}=mc^{2}/\hbar$ in its rest frame, such oscillations are too fast to directly detect ($3\times10^{25}$ Hz for 133Cs). We use an optical frequency comb and a Ramsey-Bord\'{e} matter-wave interferometer to stabilize an oscillator to a chosen subharmonic of $\omega_{0}$ with a precision of 4 parts per billion (at 6 hours timescale). Although this is far below the precision of modern frequency standards, its precision is sufficient, in combination with the spheres constructed by the Avogadro Project, to calibrate macroscopic masses with an accuracy of 30 ppb, in terms of the second. This clock may be useful for testing fundamental physics by demonstrating that its frequency redshifts in a gravitational potential in the same way that conventional frequency standards do. Implementation of a clock referenced to the mass of an elementary particle, such as an electron or positron, could also enable new experimental tests of Lorentz and CPT symmetry. [Preview Abstract] |
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Q1.00038: COLD ATOMS, MOLECULES AND PLASMAS III |
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Q1.00039: Experimental Progress towards dual quantum degeneracy of a Li6 - Cs133 mixture Jacob Johansen, Karina Jimenez-Garcia, Colin Parker, Shih-Kuang Tung, Cheng Chin Li-Cs mixtures provide unique research opportunities due to their large mass ratio and distinct optical excitation frequencies. To study many-body physics models, it is essential to prepare such systems at ultralow temperatures. As a first step toward this goal we demonstrated a translatable dipole trap setup in which we successfully trapped both species. Here we report the progress of cooling this atomic mixture to dual quantum degeneracy by sympathetically cooling Li atoms with evaporatively cooled Cs atoms. [Preview Abstract] |
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Q1.00040: Towards a quantum gas of polar YbCs molecules R. Freytag, M. Petersen, E.A. Hinds, M. Tarbutt, K. Butler, S. Kemp, S.A. Hopkins, D.A. Brue, J.M. Hutson, S.L. Cornish The potentials of ultracold polar molecules have been discussed with respect to quantum information processing and quantum simulation. This experiment focuses on the production of quantum degenerate YbCs molecules. We propose to magneto-associate the atoms over a Feshbach resonance and transfer them to the ground state using Stimulated Raman Adiabatic Passage (STIRAP). Ground state YbCs will, due to its single valence electron, exhibit an electric as well as a magnetic dipole moment. It should therefore demonstrate spin dependent interactions in addition to long-range dipole-dipole interactions. Here we outline the theoretical and experimental progress on creating a dual species Magneto-Optical Trap (MOT) of Yb and Cs. [Preview Abstract] |
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Q1.00041: Scheme for Launching and Observing Dynamics of Cold Atoms in Rydberg States Anne Goodsell, Erik Weidner, Mattias Fitzpatrick We are assembling a source of laser-cooled Rb atoms that can be launched at slow, controlled velocities and excited into Rydberg states. We assess the feasibility of detecting the motion of cold Rydberg atoms around a macroscopic charged wire. The capture and ionization of cold ground-state atoms in a $1/r$-electric field has been observed previously [1], using a nanowire to ensure that captured atoms could move in free space at small radial distances before impacting the wire or field-ionizing near the surface. Using highly-excited atoms instead, we suggest that a macroscopic wire offers a robust system with magnified effects. The capture cross-section increases for incident atoms in high-$n$ states. For a 20-micron-diameter wire charged to +300 V, the critical impact parameter for atoms traveling at 2 m/s with $n=50$ is 30 $\mu$m, 10 times larger than for ground-state atoms. We propose that aspects of this model can be realized experimentally. Using an estimated lifetime of $40$ ns for the $n=50$ state, we calculate that excitation must occur at $r$=100 $\mu$m, significantly beyond the wire's surface. In this way, we are preparing to promote launched atoms into high-$n$ states and study their dynamics. \\[4pt] [1] PRL 104, 133002 (2010). [Preview Abstract] |
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Q1.00042: Atom chip apparatus for experiments with ultracold rubidium and potassium M.K. Ivory, A.R. Ziltz, C.T. Fancher, A.J. Pyle, D. Jervis, S. Aubin We present a dual chamber apparatus for experiments with ultracold gases of $^{87}$Rb and $^{39}$K atoms on an atom chip. The apparatus produces quasi-pure Bose-Einstein condensates (BEC) of $3\times10^4$ $^{87}$Rb atoms in an atom chip micro-magnetic trap. We operate a $^{39}$K magneto-optical trap (MOT) and describe our progress toward loading these atoms into the chip trap. The apparatus features a dual-species MOT, a purely electrical magnetic transport system, and a radio-frequency (RF) capable atom chip system. The apparatus is well suited for studies of atom-surface forces, quantum pumping and transport experiments, and RF manipulation of cold atoms. We present our plans and progress for an experiment to study scattering of a BEC from an amplitude modulated barrier, a first step toward observing quantum pumping. We also detail our progress on using RF potentials for mechanical manipulation of $^{39}$K atoms at the chip. [Preview Abstract] |
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Q1.00043: Pauli Blocking Effect on 2D Trimers Near Feshbach Resonance Anffany Chen, Fei Zhou We investigate the Pauli blocking effect on 2D three-body bound states near Feshbach resonance in the presence of a Fermi sea background. We develop 2D wave equations that include the Pauli blocking effect of background fermions and obtain universal results that are fully characterized by the 2D scattering length and the Fermi wave length. This work will be a stepping stone for future more elaborated studies of 2D many-body physics, bringing us one step closer to understanding the mechanisms underlying intriguing 2D gases. [Preview Abstract] |
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Q1.00044: Equations of state and superfluid transition of a two-dimensional Bose gas Lauriane Chomaz, R\'emi Desbuquois, Tarik Yefsah, Christof Weitenberg, J\'er\^ome Beugnon, Jean Dalibard Two-dimensional (2D) systems cannot undergo phase transitions associated with continuous symmetry breaking. Nevertheless, they may exhibit a continuous transition to a superfluid phase with quasi-long range order, via the Berezinskii-Kosterlitz-Thouless (BKT) mechanism. I will present our experimental results in which we characterized the thermodynamical and dynamical properties of the 2D gas in the normal, in the critical and in the superfluid regions. Using local density approximation (LDA) and density measurement in a trapped quasi-2D gas, we infer equations of state for the homogeneous 2D gas and compare them to theories. We confirm the predicted scale invariance and identify a critical region in terms of the unique dimensionless parameter $\mu/k_B T$, ratio of the chemical potential $\mu$ on the temperature $T$. We also probe the transport properties of our gases according to $mu/k_B T$ by stirring a micron-sized obstacle on circular trajectories centered on the cloud. We measure the heating generated by the stirring at the radius $r$ and using LDA, deduce the heating behavior of the homogeneous gas at the corresponding chemical potential $\mu(r)$. We identify a transition from a normal dissipative regime to a superfluid frictionless behavior at critical $mu/k_B T |_c$. [Preview Abstract] |
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Q1.00045: Toward polar molecules from ultracold mixture of $^{23}$Na and $^{87}$Rb atoms Fudong Wang, Dezhi Xiong, Xiaoke Li, Dajun Wang The bosonic NaRb molecule has a large electric dipole moment and is stable against two body chemical reactions. It is thus well suited for studying quantum gases with dipolar interactions. We have built a compact experiment setup based on a single UHV chamber to investigate the production of this molecule by association of ultracold atoms. A dual Bose-Einstein condensate of Na and Rb has been realized with evaporative and sympathetic cooling in this setup. Interspecies Feshbach resonances are also observed and well understood. We are currently working on the formation of NaRb Feshbach molecules and the excited-state spectroscopy for producing ground-state polar molecules. [Preview Abstract] |
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Q1.00046: Superfluid Atom Circuits Jeffrey Lee, Avinash Kumar, Stephen Eckel, Fred Jendrzejewski, William Phillips, Gretchen Campbell, Christopher Lobb, Wendell Hill, III We have constructed basic atom circuits using all optical potentials on an ultracold sodium gas. In the thermal case, we have shown that these circuits contain a structure that is analogous to resistance. In the case of the BEC, where we have a superfluid, it is less clear what the proper analogy is. We will show our progress toward creating this system, and fully exploring its dynamics. [Preview Abstract] |
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Q1.00047: A compact single-chamber apparatus for Bose-Einstein condensation of $^{87}$Rb Tobias Schmidutz, Igor Gotlibovych, Stuart Moulder, Robert Campbell, Naaman Tammuz, Richard Fletcher, Alexander Gaunt, Scott Beattie, Robert Smith, Zoran Hadzibabic We describe a simple and compact single-chamber apparatus for robust production of $^{87}$Rb Bose-Einstein condensates. The apparatus is built from off-the-shelf components and allows production of quasi-pure condensates of $ > 3 \times 10^5 $ atoms in $<$ 30 s. This is achieved using a hybrid trap created by a quadrupole magnetic field and a single red-detuned laser beam [Y.-J. Lin et al., Phys. Rev. A 79, 063631 (2009)]. In the same apparatus we also achieve condensation in an optically plugged quadrupole trap [K. B. Davis et al., Phys. Rev. Lett. 75, 3969 (1995)] and show that as little as 70 mW of plug-laser power is sufficient for condensation, making it viable to pursue this approach using inexpensive diode lasers. While very compact, our apparatus features sufficient optical access for complex experiments. [Preview Abstract] |
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Q1.00048: Finite-temperature properties of small trapped two-component Fermi gases: Tan contact and statistics Yangqian Yan, D. Blume We consider equal-mass two-component Fermi gases under external spherically symmetric confinement for which the unlike atoms interact via a short-range Gaussian potential with a diverging $s$-wave scattering length. Using the path integral Monte Carlo technique, the thermodynamics of systems with up to ten particles is studied over a wide temperature range. We present results for the pair distribution function and the internal energy. We determine Tan's contact by analyzing pair distribution functions for various temperatures as a function of the range of the underlying two-body potential. For the three- and four-particle systems, comparisons with results obtained by alternative approaches are presented. Lastly, we ``turn off'' permutations and determine the temperature regime in which exchange effects are negligible. [Preview Abstract] |
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Q1.00049: Experimental investigation of dynamics in spin-orbit coupled BECs. Chris Hamner, Peter Engels In this poster we will present results from a Bose-Einstein condensate (BEC) experiment at WSU studying dynamics of spin-orbit coupled $^{87}$Rb BECs. Ultra-cold atomic gases provide a very promising setting for such studies because of the high tunability and precise characterization of system parameters. We will describe our experimental setup as well as results from a recent study of spin dynamics induced by quantum quenches. [Preview Abstract] |
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Q1.00050: Towards quantum simulation and quantum sensing with strontium and lithium Ruwan Senaratne, Shankari Rajagopal, Zachary Geiger, Vyacheslav Lebedev, David Weld In this poster we describe progress towards the construction of two ultracold atomic physics experiments, based on bosonic and fermionic strontium and lithium. Applications of the experiments will include quantum simulation of quasicrystals, the development of novel cooling techniques, and force sensing on small length scales. We discuss hardware design, experimental features, and scientific goals. [Preview Abstract] |
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Q1.00051: Radio-Frequency Spectroscopy of a Mass-Imbalanced Fermi-Fermi Mixture: Measuring Atom-Dimer Interactions Marko Cetina, Michael Jag, Matteo Zaccanti, Rianne Lous, Jesper Levinsen, Dmitry Petrov, Florian Schreck, Rudolf Grimm We use radio-frequency spectroscopy to investigate a mixture of $^{40}$K atoms and $^{6}$Li$^{40}$K Feshbach molecules on the repulsive side of a $^{6}$Li-$^{40}$K Fermi-Fermi interspecies Feshbach resonance. The shifts in the peak positions in our spectra indicate an attractive interaction between the $^{40}$K atoms and $^{6}$Li$^{40}$K dimers, related to a $p$-wave atom-dimer scattering resonance. The measured attraction agrees well with a mean field description of the atom-molecule interaction, even in the strongly-interacting regime. Strong tails in our spectra point to the importance of momentum corrections to the wavefunction of the interacting K atoms and provide information about the excited states of our system. [Preview Abstract] |
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Q1.00052: Realizing Fractional Chern Insulators in Dipolar Systems Norman Yao, Alexey Gorshkov, Chris Laumann, Andreas Lauchli, Jun Ye, Mikhail Lukin Strongly correlated quantum systems can exhibit exotic behavior controlled by topology. We predict that the $\nu=1/2$ fractional Chern insulator arises naturally in a two-dimensional array of driven, dipolar-interacting spins. As a specific implementation, we analyze how to prepare and detect synthetic gauge potentials for the rotational excitations of ultra-cold polar molecules trapped in a deep optical lattice. With the motion of the molecules pinned, under certain conditions, these rotational excitations (acting as effective spins) form a fractional Chern insulating state. We present a detailed experimental blueprint for its realization and demonstrate that the implementation is consistent with near-term capabilities. Prospects for the realization of such phases in solid-state dipolar systems are discussed as are their possible applications. [Preview Abstract] |
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Q1.00053: Exploring cavity-mediated long-range interactions in a dilute quantum gas Renate Landig, Rafael Mottl, Ferdinand Brennecke, Kristian Baumann, Tobias Donner, Tilman Esslinger We report on the observation of a characteristic change in the excitation spectrum of a Bose-Einstein condensate and increased density fluctuations due to cavity-mediated atom-atom interactions. Increasing the strength of the interaction leads to a softening of an excitation mode at finite momentum, preceding a superfluid to supersolid phase transition. The observed behavior is reminiscent of a roton minimum, as predicted for quantum gases with long-range interactions. We create long-range interactions in the BEC using a non-resonant transverse pump beam which induces virtual photon exchange via the vacuum field of an optical cavity. The mode softening is spectroscopically studied across the phase transition using a variant of Bragg spectroscopy. At the phase transition a diverging density response is observed which is linked to increased density fluctuations. Using the cavity dissipation channel we monitor these fluctuations in real-time and identify the influence of measurement backaction onto the critical behavior of the system. [Preview Abstract] |
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Q1.00054: In situ imaging of a lattice Bose gas via Raman cooling Srivatsan Chakram, Lauren Aycock, Benjamin Nosarzewski, Mukund Vengalattore We present experimental results on the non-destructive imaging of a lattice Bose gas via fluorescence induced by two-photon transitions. We first realize rapid, all-optical Bose condensation of $^{87}$Rb atoms through a combination of degenerate Raman sideband cooling and adiabatic manipulations of an optical dipole trap. The atoms are then confined in a far off-resonant optical lattice and subjected to a periodically modulated two-photon transition. This sequence has the combined effect of inducing fluorescence in the confined atoms while simultaneously cooling them to the ground state of the lattice. In contrast to the demonstrated lattice imaging techniques [1,2], our technique can be extended to atomic species that are less amenable to polarization-gradient cooling. In addition, the minimally destructive nature of our technique allows the time-resolved studies of such lattice-based atomic systems. The high rates of data acquisition, large condensed ensembles and non-destructive imaging techniques demonstrated in our system are ideally suited for metrology and studies of non-equilibrium many-body dynamics using degenerate atomic gases\\[4pt] [1] W. Bakr {\em et al}, Nature \textbf{462}, 72 (2009);\\[0pt] [2] J. F. Sherson {\em et al}, Nature \textbf{467}, 68 (2010); [Preview Abstract] |
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Q1.00055: Topological order in 1D super-lattice Bose-Hubbard models Michael Fleischhauer, Fabian Grusdt, Michael Hoening After the discovery of topological insulators as a new state of matter and their consequent classification for free fermions, the question arises what kind of topological order can be supported by incompressible systems of interacting bosons. We consider a 1D super-lattice Hamiltonian with a non-trivial band structure (the Su-Schrieffer-Heeger model) and show that its Mott-insulating (MI) states can be classified by a quantized many-body winding number. This quantization is protected by sub-lattice and time-reversal symmetries, and it allows the implementation of a quantized cyclic pumping process (Thouless pump) in a simple super-lattice Bose-Hubbard model (BHM). For extended BHMs we discuss a connection of such a pump with the fractional quantum Hall effect. Furthermore we show that the quantization of the winding number leads to localized, protected edge states at sharp interfaces between topologically distinct MI phases which can be experimentally realized using Bose-Fermi mixtures in optical superlattices. DMRG simulations show that these edge states manifest themself either in localized density maxima or localized density minima, which can easily be detected. [Preview Abstract] |
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Q1.00056: Engineering Dirac points with ultracold fermions in a tunable-geometry optical lattice Daniel Greif, Thomas Uehlinger, Gregor Jotzu, Leticia Tarruell, Tilman Esslinger Dirac points lie at the heart of many fascinating phenomena in condensed matter physics, ranging from massless electrons in graphene to the emergence of conducting edge states in topological insulators. At a Dirac point, two energy bands intersect linearly and the particles behave as relativistic Dirac fermions. A highly flexible approach to studying Dirac points is to create model systems using ultracold fermionic atoms trapped in the periodic potential of interfering laser beams. In our setup we have realized an optical lattice of tunable geometry, ranging from square, triangular, honeycomb, dimer and different one-dimensional structures. For the case of the honeycomb lattice, we probe the band structure using momentum resolved interband transitions and observe the appearance of Dirac points with tunable properties. Furthermore, recent progress on the interplay between geometry and interactions will be presented. [Preview Abstract] |
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Q1.00057: Measuring contact dynamics of a Fermi gas at a Feshbach resonance Chris Luciuk, Alma Bardon, Dan Fine, Nathan Cheng, Scott Beattie, Stefan Trotzky, Joseph Thywissen In 2005, S. Tan derived a series of universal relations for strongly interacting Fermi gases built around a single central parameter called the ``contact.'' Subsequently, the contact parameter has been measured in experiments with trapped ultracold Fermi gases, allowing for a verification of some of these relations. We use quantum degenerate clouds of K-40 to study the non-equilibrium dynamics of the contact, initialized in either a coherent superposition or in an incoherent mixture of two different internal states. In the superposition case, we find the contact dynamics to be connected to the single-particle coherence dynamics. We make use of a Feshbach resonance to tune the interactions of the Fermi gas and find the short-time dynamics to be different in the BEC and BCS regime. When the superposition has fully decohered, the time-evolution is governed by atom loss to a molecular bound state. We discuss our measurement technique, including cooling {\&} initialization, fast RF spectroscopy, and spin-resolved imaging. [Preview Abstract] |
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Q1.00058: Superfluid Density of Weakly Interacting Bosons on a Lattice Yariv Yanay, Erich Mueller We use a path integral approach to calculate the superfluid density of a Bose lattice gas in the limit where the number of atoms per site is large, for one component and two component gases. The results for a one-component gas agree with calculations done by other methods such as a Gutzwiller-ansatz calculation. In the two component case, we find that the interaction between atom species can increase the superfluid density of both, even if the cross-species superfluid drag remains small. Our approach builds on similar calculations done without a lattice. To attain the correct results we develop tools for calculating discrete time path integrals which are applicable to a range of systems naturally described within an overcomplete basis. [Preview Abstract] |
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Q1.00059: An Experimental Apparatus for Studying Strongly Correlated States of Rydberg Polaritons Alex Georgakopoulos, Albert Ryou, Jia Ningyuan, Jonathan Simon We describe a hybrid apparatus for generation and manipulation of strongly correlated states of Rydberg polaritons. By combining a high-finesse optical resonator with a Rydberg-dressed gas of 87Rb atoms, it will be possible to achieve optical depths per blockade radius of order 10$^4$, permitting, for the first time, strong, lossless interactions between polaritons. We will discuss accessible physics, including quantum crystallization, topological phases, and high-fidelity quantum information processing. Furthermore, we will present, in detail, technical pitfalls and their resolutions, focusing in particular on electric-field- and vibration- suppression, and a state-of-the art laser system for generating the Rydberg excitations, controlling the cavity, and detecting the resulting manybody states. [Preview Abstract] |
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Q1.00060: Collapse and Revival for Double-Well Superlattices Lei Jiang, Eite Tiesinga, Philip Johnson Collapse and revival experiments with ultracold atoms in single-well optical lattices are a great demonstration of matter-wave interference. In fact, this interference could be used to measure the interaction strength between atoms. Experiments nowadays have the possibility to form double-well superlattices as well. Here, we discuss theoretically the physics of collapse and revival for double-well superlattices. Different parameter regions of lattice depth as well as tilt between the two wells have been explored focusing on the timescales in which lattices need to be deformed such that unwanted excitations are avoided. We also derive effective multi-body interactions in the double well system. [Preview Abstract] |
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Q1.00061: Light scattering in dense and cold $^{87}$Rb Kasie J. Haga, S.J. Roof, S. Balik, M.D. Havey, Igor M. Sokolov, Dimitriy V. Kupriyanov Quantum optics in ultracold and high-density, but non quantum degenerate, atomic gases is a promising area of research. Studies of quantum hologram creation in optically dressed samples, enhanced molecule formation, and ultracold plasma physics in the strongly coupled regime are intriguing areas of current activity. Exploration of the role of spatial disorder on light propagation in such systems and disorder-mediated formation and manipulation of subradiant and superradiant configurations are topics of considerable interest. In this paper we present experimental results on light scattering in a cold and quite high density gas of $^{87}$Rb atoms. The sample is prepared in an optical dipole trap, and has a peak density $\sim$ 6 $\cdot$ $10^{13}$ atoms/cm$^{3}$ and a temperature $\sim$ 60 $\mu K$. Here the $F=2\to F'=3$ nearly closed hyperfine transition is studied. We discuss two experimental geometries. In one, near-resonance radiation is directed towards the sample; the response is recorded as a function of time and frequency. In a second, the probe beam is overlapped with a far off resonance light shift laser, which reduces the optical depth through the central region of the sample, allowing for generation of a quasi one dimensional configuration. [Preview Abstract] |
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Q1.00062: Ultracold Mixtures of Lithium and Ytterbium Anders Hansen, Alexander Khramov, William Dowd, Richard Roy, Alan Jamison, Benjamin Plotkin-Swing, Subhadeep Gupta Quantum degenerate mixtures of alkali and alkaline-earth-like atoms introduce a wide range of studies of few- and many-body physics, and provide a path toward paramagnetic, polar molecules. We here report on our production and studies of a novel ultracold-atom system comprised of a mixture of ground-state $^{6}$Li, and $^{174}$Yb in the metastable $^{3}P_{2}$-state. This mixture has the advantage over ground-state Li+Yb of potentially exhibiting wide magnetically tunable interactions, and is predicted to possess a far greater dipole moment. We also discuss recent studies of chemical dynamics near the broad $^{6}$Li Feshbach resonance, as modified by a third, non-resonant species, including measurements of reaction rate coefficients and their comparison with theoretical scattering length-dependent scaling laws. [Preview Abstract] |
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Q1.00063: Universal properties of the three-body scattering length and its relation to Efimov physics Jose P. D'Incao, Chris H. Greene In this work we study elastic properties involving three free atoms in the regime in which the interatomic interactions are strongly affected by a Feshbach resonance. Using the hyperspherical adiabatic representation we have determined the corresponding three-body scattering length and explore its connections with the energy levels of three particles in a harmonic trap. In particular, we study the relation between the three-body scattering length and the energy levels in the trap when the two-body scattering length is tuned near a Efimov resonance. [Preview Abstract] |
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Q1.00064: Dipolar OH dynamics in a magnetic trap and electric field Goulven Qu\'em\'ener, John Bohn Recently, evaporative cooling of OH radicals have been achieved in a magnetic trap [1]. To understand the dynamics of the gas of molecules inside the trap as it cools down, and/or to understand the loss of molecules when an additional external electric field is turned on, we have to perform a full dynamics calculation using Monte Carlo simulation types. Before this step, we need to know in which directions the molecules are scattered after a collision. For this purpose we will present a calculation of the elastic and inelastic differential cross sections of OH + OH collisions at low and ultralow energies, for different configurations of electric and magnetic fields, and if time, include them in a Monte Carlo simulation to describe the overall dynamics.\\[4pt] [1] Benjamin K. Stuhl, Matthew T. Hummon, Mark Yeo, Goulven Qu\'em\'ener, John L. Bohn, Jun Ye, Nature {\bf 492}, 396 (2012). [Preview Abstract] |
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Q1.00065: Radiative charger transfer in ultracold collisions of Yb atoms and Rb ions Brendan McLaughlin, Hugo Lamb, Jim McCann We have investigated radiative decay processes at ultra-cold temperatures and above for Rb ions colliding with Yb atoms. Previously [1], we investigated the structure and low temperature dynamics of Yb atoms colliding with R ions. We use the MOPRO quantum chemistry suite of codes to obtain potential energies and transition dipole moments, as a function of bond length between low lying states of the YbRb$^+$ molecular ion complex. A full-configuration interaction (FCI) and a multi-reference configuration interaction (MRCI) approximation is use to determine all the potential energy curves and moments, where the molecular orbitals (MO's) used are obtained from state averaged multi-configuration-self-consistent field (MCSCF) calculations. The collision problem is solved quantally using an optical potential method with a semi-classical approximation invoked for higher energies. Rate coefficients are determined for temperatures ranging from micro-Kelvin up to 20, 000 Kelvin. Further details and a comprehensive set of results will be presented at the meeting.\\[4pt] [1] H. D. J. Lamb, J. F. McCann, B. M. McLaughlin, J. Goold, N. Wells and I. Lane, Phys. Rev. A 86, 0227719 (2012). [Preview Abstract] |
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Q1.00066: A new optical trap and repump system for ultracold Strontium Y. Huang, M. Yan, B.J. DeSalvo, T.C. Killian Atoms can be trapped at the foci of intense laser beams, which can enable the study of interactions and dynamics of ultracold gases. In this poster, we will describe our new trap design. A large volume pancake-shaped optical dipole trap is initially used for loading large numbers of atoms from a Magneto-Optical Trap. Atoms are then evaporatively cooled and compressed into a superimposed crossed-beam dimple trap. This combination improves the reproducibility of the experiment and shortens the time required to create quantum degenerate samples. In the second part of the poster, we will discuss a new repump scheme for laser cooling of Sr that uses the 5s5p$^{3}$P$_{2-}$5p$^{2\, 3}$P$_{2}$ transition at 481nm. The availability of laser diodes at this wavelength makes this an appealing alternative to other schemes. [Preview Abstract] |
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Q1.00067: Optimizing Bichromatic Force Decelerators for Atoms and Molecules Scott Galica, Leland Aldridge, Kurt Nesteruk, Michael Chieda, Edward Eyler Optical bichromatic forces (BCFs) have shown success in slowing atomic beams,\footnote{M. A. Chieda and E. E. Eyler, PRA \textbf{86}, 053415 (2012), and references therein.} and they have considerable promise for laser slowing of molecules. Our first-generation BCF decelerator for metastable helium has achieved slowing by $>$500~m/s in less than 5~cm using ordinary diode lasers, with He* brightness similar to a Zeeman slower. We discuss explorations of atomic and molecular evolution under multicolor illumination with a view towards optimizing decelerators for MOT loading. These explorations include numerical studies of the excited-state fraction for two-level atoms in bichromatic and polychromatic light, progress towards a multi-level simulation for testing molecular behavior, and continuing investigations of the large-detuning limit of the BCF magnitude. We also discuss progress in developing a practical BCF decelerator for molecules, which could substantially improve on recent results using Doppler and Sisyphus forces.\footnote{J. F. Barry, \textit{et al.}, PRL \textbf{108}, 103002 (2012); M. Zeppenfeld, $et. al.$, Nature \textbf{491}, 570 (2012).} Our initial experimental configuration is a BCF-based beam deflector for CaF molecules. [Preview Abstract] |
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Q1.00068: Progress towards a degenerate gas of strontium D.S. Barker, B.J. Reschovsky, J.A. Pechkis, N.C. Pisenti, G.K. Campbell We report on progress towards creating degenerate gases of strontium for use in optical lattice experiments. We have recently created and characterized a MOT capable of trapping either $^{87}$Sr or $^{88}$Sr on the broad, 461 nm cycling transition. Our diagnostics focus on using the MOT as a source of cold $^{3}P_2$ atoms, which are continuously loaded into a magnetic trap. We also investigate sub-Doppler cooling of the fermionic isotope and the possibility of loading these atoms directly into an optical dipole trap. [Preview Abstract] |
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Q1.00069: Magic optical trapping of Rydberg atoms Siyuan Zhang, Gang Li, Larry Isenhower, Mark Saffman We demonstrate trapping of both ground and Rydberg excited Cesium atoms in an optical bottle beam trap. The trap is generated by crossing two tightly focused Laguerre-Gaussian LG$_{01}$ beams. This generates a dark region completely surrounded by light which is needed to trap Rydberg states which have negative polarizability. If the wavelength of light is chosen to also have a negative polarizability for the ground state then both states will be trapped. We demonstrate a trap lifetime for the Cs 61d$_{3/2}$ state of $360~\mu\rm s$ and a trap induced ground-Rydberg transition shift on the order of 100 kHz. [Preview Abstract] |
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Q1.00070: Near ground state Raman sideband cooling of an ion in a hybrid radiofrequency-optical lattice trap Alexei Bylinskii, Leon Karpa, Dorian Gangloff, Marko Cetina, Vladan Vuletic We achieve near ground state cooling of an ion in a hybrid trap formed by a two-dimensional radio-frequency Paul trap and an optical lattice produced by a cavity in the axial dimension. We drive far-detuned lattice-assisted Raman transitions on the red vibrational sideband between the Zeeman sublevels of the $^{2}$S$_{1/2}$ ground level of $^{174}$Yb$^{+}$. The cooling cycle is completed by a close-detuned spontaneous Raman transition. Efficient Cooling in all three dimensions is achieved this way. Furthermore, spatially dependent AC Stark shifts induced by the lattice allow us to measure axial temperature via ion fluorescence, and we estimate the population of the lattice vibrational ground state to be above 50{\%}. This work is an important step towards quantum information and quantum simulations with ions in hybrid traps and optical lattices. [Preview Abstract] |
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Q1.00071: Adiabatic Rapid Passage Forces for Laser Cooling John Elgin, Harold Metcalf Optical forces from Adiabatic Rapid Passage (ARP) have been shown to be significantly larger than the ordinary radiative force even outside the usual adiabatic parameter range of $\Omega_0 \sim \delta_0 \gg \omega_m \gg \gamma$. Here $\Omega_0$ is the peak Rabi frequency, $2 \delta_0$ is the sweep range, $\omega_m$ is the repetition rate, and $\tau \equiv 1/\gamma$ is the excited state lifetime. For ARP to be useful for laser cooling it needs to be not only strong, but also dependent on atomic velocity $v$. We have shown preliminary $v$-dependent measurements with an apparatus having two independent counter-propagating chirped pulses. Having further improved our ability to measure and control the pulse shape and frequency chirp we present our newest $v$-dependent data and draw some comparisons between ARP and the bichromatic force. [Preview Abstract] |
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Q1.00072: Applications of Atom Trap Trace Analysis in the Earth Sciences Z.-T. Lu, W. Jiang, K. Bailey, P. Mueller, T.P. O'Connor With the successful development of the Atom Trap Trace Analysis (ATTA) method, radiokrypton dating has become available for the first time to the Earth science community at large. This novel tool is enabling new research opportunities and improved understanding in the Earth sciences, with implications in studying climate change and in water resource management. Examples of applications of ATTA in the Earth sciences are: (1) ATTA measurements of $^{81}$Kr in the Nubian Aquifer of Africa, the Great Artesian Basin of Australia, and the Guarani Aquifer of South America have transformed our understanding of the long-term behavior of these large aquifer systems. $^{81}$Kr dating with more extensive sampling will be carried out on major aquifer systems around the world. (2) A systematic survey of $^{39}$Ar throughout the oceans, particularly when combined with $^{14}$C data, will fill major gaps in our knowledge of deep ocean circulation and mixing, and will allow more accurate predictions of oceanic sequestration of atmospheric CO$_2$. (3) The feasibility and accuracy of $^{81}$Kr dating of old ice has been tested with the well-dated stratigraphy of Taylor Glacier in Antarctica. For more information, search for ``TANGR2012''. [Preview Abstract] |
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Q1.00073: Progress Toward Coupling a Sample of Collectively Excited Atoms to a High Finesse Cavity Patrick Zabawa, Charles Ewel, Harald Kuebler, Shaffer James Rydberg atom blockade, a phenomenon in which the excitation of more than one Rydberg atom in a certain radius is blocked due to long-range dipole-dipole and van der Waals forces, can be used to produce collective excitations within a sample of atoms. Given a small sample size and large blockade radius, this technique can be used to create non-classical states of light with a few or single photons without the need for addressing individual atoms. We report on our progress in the design and construction of an apparatus that will exploit the Rydberg blockade effect in a sample of ultracold $^{87}$Rb atoms that is confined to the mode of a high finesse optical cavity. Magnetic transport will be used to move atoms from a magneto-optical trap to the cavity. Early experiments will involve confirmation of the Rydberg blockade effect, testing the magnetic transporter, and characterization of the coupling between the optical cavity and the sample. [Preview Abstract] |
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Q1.00074: Towards exciting a Rydberg gas in optical lattices. Manukumara Manjappa, Jingshan Han, Ruixiang Guo, Thibault Vogt, Wenhui Li Rydberg atoms are highly excited atoms with principal quantum number n \textgreater 10. They have exaggerated properties such as large dipole moment and high polarizability. Large dipole-dipole interactions between Rydberg atoms, which lead to Rydberg blockade and giant non linearity, provide unique opportunities for studying quantum many-body physics [1-3]. Rydberg excitation of ground state quantum gas in optical lattices has already shown the formation of spatially organized structures [2] and Rydberg dressed systems are promising for entering the strongly correlated regime [3]. Our current project is to study the collective excitation to Rydberg states from a quantum gas of ground state atoms in an optical lattice. In this poster we present the latest development in building up the experimental apparatus and our plans on spectroscopic measurements and spatially imaging of Rydberg excitations.\\[4pt] [1] Weimer, H., et al. (2010). Nature Physics 6(5): 382-388.\\[0pt] [2] Schausz, P., et al. (2012). Nature 491(7422) 87-91.\\[0pt] [3] Pupillo, G., et al. (2010). PRL 104(22) 223002. [Preview Abstract] |
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Q1.00075: Coherence on F\"{o}rster resonances between Rydberg atoms Robert Loew, Alexander Krupp, Johannes Nipper, Jonathan Balewski, Tilman Pfau F\"{o}rster resonances are non-radiative dipole-dipole interactions between oscillating dipoles. Especially in biochemistry these resonances play a crucial role and describe the energy transfer process in many systems. In our work these resonances occur between pairs of Rydberg atoms, creating strong interactions between the atoms. We report on studies of F\"{o}rster resonances between Rydberg atoms in an ultra-cold atomic cloud of 87Rb. By applying a small electric field we tune dipole coupled pair states into resonance, giving rise to F\"{o}rster resonances. Via a Ramsey-type atom interferometer we can resolve several resonances at distinct electric field strengths. We study the coherence of the system at and close to the resonances and we observe a change in phase and visibility of the Ramsey fringes on resonance. The individual resonances are expected to exhibit different angular dependencies, opening the possibility to tune not only the interaction strength but also the angular dependence of the pair state potentials by an external electric field. Nipper et. al. Phys. Rev. Lett. 108, 113001 (2012) Nipper et. al. Phys. Rev. X 2, 031011 (2012); [Preview Abstract] |
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Q1.00076: Computational studies of dipole-dipole interactions among Stark manifold states Thomas Carroll, Alexander R. Mellus, Alexander M. Chartrand, Donald P. Fahey, Michael W. Noel In our experiment, we excite ultra-cold atoms in a magneto-optical trap to Rydberg states in a Stark manifold ($n \sim 35$). An external electric field tunes the states such that a pair of atoms can resonantly exchange energy. One atom transitions to the $(n+1)$ manifold and the other to the $(n-1)$ manifold. We present the results of a computational model of this interaction which includes as many as 6 atoms. We examine many-body effects and redistribution of initial atomic population among the densely packed manifold states. [Preview Abstract] |
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Q1.00077: Expansion of an ultracold plasma affected by spatial correlation and the delayed injection of charged particles Hossein Sadeghi, Markus Schulz-Weiling, Jachin Hung, Jack Warren, Nicolas Saquet, Jonathan Morrison, Edward Grant A dense Rydberg gas of nitric oxide formed in a supersonic molecular beam evolves on a tens of nanoseconds timescale to form an ultracold plasma. Images of electron density recorded as a function of flight time gauge the rate of plasma expansion. Over regions of Rydberg gas density well matched to the selected initial principal quantum number, dissociation of deactivated Penning partners depletes the distribution of nearest neighbours, giving rise to a gas of spatially correlated ions, which has a discernible effect on plasma expansion and durability in a pulsed electrostatic field. Post-avalanche injection of hot electrons and stationary ions or stationary Rydberg molecules affects plasma expansion in distinctive ways. Model calculations describe the potential energy characteristics of the Penning lattice and couple the kinematics of an initial ambipolar expansion to those of subsequently added charged particles with positive or negative energy. [Preview Abstract] |
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Q1.00078: Nanostructured Diamond for Enhanced Collection Efficiency from NV Centers Brendan Shields, Nathalie de Leon, Alexander Zibrov, Hongkun Park, Mikhail Lukin Nitrogen-vacancy (NV) centers in diamond are at the heart of a growing number of promising technologies, ranging from field sensing to solid-state quantum repeaters. Key to these applications is the ability to read out the electronic spin state accurately via the NV's optical transition. Here we present a method for enhanced photon collection efficiency from NVs near the interface between a diamond nanobeam and a glass plate. [Preview Abstract] |
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Q1.00079: Quantum nanophotonics with nitrogen vacancy centers in diamond Yiwen Chu, Nathalie de Leon, Ruffin Evans, Birgit Hausmann, Brendan Shields, Michael Burek, Matthew Markham, Alastair Stacey, Daniel Twitchen, Hongkun Park, Marko Loncar, Mikhail Lukin Individual color centers in diamond have emerged as a promising solid-state platform for quantum communication and quantum information processing systems, as well as sensitive nanoscale magnetometry with optical read-out. Engineering the light-matter interaction between defect centers and nanophotonic devices can greatly enhance the performance of these systems. We demonstrate individual Nitrogen-Vacancy (NV) centers embedded in nanofabricated hybrid photonic crystal cavities consisting of single crystal diamond and PMMA based Bragg structures. Devices with quality factors up to 3,000 coupled to NV centers have been obtained, leading to Purcell factors of up to 14. We also investigate the optical coherence properties of NV centers inside these nanoscale structures. These nanophotonic devices could potentially enable strong coupling between the cavity field and NV centers as well as enabling applications such as quantum networks and single photon transistors. [Preview Abstract] |
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Q1.00080: Autoionization resonances of lanthanide ions in the vicinity of 6.X nm spectral range Sindhu Kalyadan, A. Kumar, H.R. Varma, P. Hayden, J.T. Costello, P.C. Deshmukh We report autoionization resonance studies of some lanthanide ions in the vicinity of the 6.X nm spectral range. Studies of the resonances in this spectral range have attracted considerable attention recently due to their importance in developing next generation extreme ultraviolet (EUV) lithography light sources [1, 2]. The resonance structures result from the interference of ``bound to continuum'' ionization channels from the 5s subshell and the ``bound to bound'' excitation channels from the 4d subshells of some of the lanthanide ions. We employ the relativistic random phase approximation (RRPA) [3] to obtain multichannel quantum defect parameters and then use the relativistic multichannel quantum defect theory (RMQDT) [4] to investigate the autoionization resonances in Ce XI, La X and Pr~XII.\\[4pt] [1] S. S. Churilov, R. R. Kildiyarova, A. N. Ryabtsev and S. V. Sadovsky, Phys. Scr. {\bf 80}, 045303 (2009)\\[0pt] [2] D. Kilbane and G. O'Sullivan, Phys. Rev. A. {\bf 82}, 062504 (2010)\\[0pt] [3] W. R. Johnson, C. D. Lin, K. T. Cheng and C. M. Lee, Phys. Scr. {\bf 21}, 409 (1980)\\[0pt] [4] C. M. Lee ad W. R. Johnson, Phys. Rev. A {\bf 22}, 979 (1980) [Preview Abstract] |
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Q1.00081: Double Photoionization of C$^{2+}$ M.S. Pindzola, Sh. A. Abdel Naby, J. Colgan A time-dependent close-coupling method is used to calculate the single photon double ionization of C$^{2+}$ in support of a planned experiment at FLASH/DESY using an EBIT. At a photon energy of 125 eV the two outgoing electrons share an energy of 12.3 eV. Energy and angle differential cross sections are calculated to fully investigate the correlated motion of the two photoelectrons. [Preview Abstract] |
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Q1.00082: THE IRON OPACITY PROJECT: High-Energy-Density Plasma Opacities E. Palay, C. Orban, S. Nahar, A. Pradhan, M. Pinnsonoault, J. Bailey Opacity governs radiation flow in plasma sources. Accurate opacities are needed to model unobservable laboratory and astrophysical conditions. High-energy-density (HED) plasma conditions prevalent in stellar interiors can now be recreated in the laboratory. The Z-pinch fusion device at the Sandia National Lab can reproduce temperatures and densities near the boundary where radiation transport changes from diffusion to convection inside the Sun. To benchmark theoretical opacities experiments are essential to resolve the outstanding discrepancy in solar abundances. The most common volatile elements C, N, O, Ne, etc. have been spectroscopically measured to be up to 50\% lower than the standard abundances. This introduces conflict in the derived values of basic solar parameters such as the radiation/convection boundary, sound speed, and the primordial He abundance with precisely measured oscillations of the Sun through Helioseismology. A potential solution is increment of stellar opacities, which has inverse but complex relation with abundacnes, at least 30\%. New iron opacity calculations include hitherto neglected atomic physics of fine structure and resonances which are largely treated as lines in existing opacities calculations. Preliminary results on radiative transitions in Ne [Preview Abstract] |
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Q1.00083: Soft X-ray Instruments at LCLS-II John Bozek, Christoph Bostedt The LCLS x-ray free electron laser (FEL) at SLAC National Accelerator Laboratory is being upgraded to include two additional FELs over the next four years. The soft x-ray instruments will be moved to one of these new sources and a new suite of beamlines and instruments will be built. A description of the capabilities of the source and the new beamlines will be presented. [Preview Abstract] |
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Q1.00084: Analysis of resonances for the inner-shell 2$p$ photoionization of Mg Prabha Padukka, Hsiao-Ling Zhou, Steven T. Manson The photoionization cross section of the inner-shell 2$p$ of Mg has been calculated using the R-matrix method with LS coupling. The discrete Mg$^{+}$ orbitals are generated using Hartree-Fock (HF) and multiconfiguration HF (MCHF) programs. Based on the photoionization cross section calculation, an eigenphase derivative technique, the QB method [1], along with quantum defect theory were employed to obtain the resonance positions and effective quantum numbers (quantum defects) of the lower members of various autoionizing series including$^{\thinspace }$\textit{2p}$^{5}$\textit{3s}$^{2}$\textit{nl }converging to the \textit{2p}$^{5}$\textit{3s}$^{2}$ threshold, and \textit{2p}$^{5}$\textit{3snln'l'} above the \textit{2p}$^{5}$\textit{3s}$^{2}$ threshold over the 55 eV to 70 eV photon energy range. Among the resonances, most are relatively narrow, except for the \textit{2p}$^{5}$\textit{3s3p}$^{2}$ which are far broader, indicating a much more rapid decay rate. This phenomenology is traced to the fact that the wide resonances occur for states in which the two excited electrons are in the same subshell so that they are physically close together and, thus, the repulsion between them is significantly larger than for resonance states with excited electrons in differing subshells. Reasonably good agreement is obtained between our calculations and the few available NIST values. This work was supported by DOE and NSF. \\[4pt] [1] L. Quigley, K. Berrington and J. Palen, Computer Phys. Commun. \textbf{114,} 225 (1998). [Preview Abstract] |
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Q1.00085: Demonstration of a rubidium fiber laser R. Ayachitula, M.K. Shaffer, Boris Zhdanov, R.J. Knize Fiber lasers over the last fifty years have become one of the most compact, efficient and cost-effective coherent light sources available. In the past decade, free-space optically pumped alkali lasers have demonstrated high efficiency and good beam quality. Alkali lasers have the advantage that they can be scaled to higher powers that fibers are adept at handling for long distances. Combining these two technologies, we report on an optically pumped alkali vapor laser in a hollow fiber where rubidium and ethane have been allowed to migrate throughout the hollow core fiber. Similar to traditional alkali lasers, we end pump rubidium in our fiber at the 780nm,~5S$_{\mathrm{1/2~}}\to $~5P$_{\mathrm{3/2~}}$D2 line,~create a population inversion between the 5P$_{\mathrm{1/2~}}$~and~ 5S$_{\mathrm{1/2~}}$states from mixing via ethane and lase on the 795nm D1 line. [Preview Abstract] |
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Q1.00086: Atomic Photoionization of Ba 5s using Relativistic Random Phase Approximation \textit{with} Relaxation Aarthi Ganesan, Sudha Deshmukh, Gagan B. Pradhan, Vojislav Radojevic, Steven T. Manson, Pranawa C. Deshmukh We report studies of photoionization cross section and angular distribution of Barium 5s using both the Relativistic Random Phase Approximation (RRPA) [1] and the Relativistic Random Phase Approximation \textit{with} relaxation (RRPA-R) [2]. It is found that agreement between theory and experiment in the region of the higher-energy 5s Cooper minimum is significantly better for the cross section when relaxation is included. The agreement between theory and experiment with regard to the angular distribution of the photoelectrons however, is only qualitatively correct; theory predicts a deviation of the $\beta $ parameter from 2 over the correct energy range, but quantitatively, theory predicts a substantially larger deviation than is seen experimentally [3]. This demonstrates that non-RPA correlations are necessary for quatitative accuracy, most likely interchannel coupling with the important ionization-plus-excitation channels in the region of this Cooper minimum. \\[4pt] [1] W. R. Johnson and C.D. Lin (1979) Phys. Rev. A \textbf{20}, 964 (1979).\\[0pt] [2] V. Radojevic, M. Kutzner and H. P. Kelly, Phys.Rev. A \textbf{40}, 727 (1989).\\[0pt] [3] S. B. Whitfield, R. Wehlitz, V. K. Dolmatov, J. Phys. B \textbf{44}, 165002 (2011). [Preview Abstract] |
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Q1.00087: Measurement of the Electron Affinity of Gallium and the Fine Structure of Ga$^{-}$ N.D. Gibson, C.W. Walter, C.T. Crocker, R.S. Ficken, J.N. Yukich The electron affinity of gallium and the negative ion fine structure splittings of Ga$^{-}$ have been measured using tunable laser photodetachment threshold spectroscopy. The relative cross sections for neutral atom production were measured with a crossed laser-ion beam apparatus over the photon energy range 0.27 -- 0.41 eV. An $s$-wave threshold was observed due to the opening of the Ga$^{-}$ (4$p^{2} {}^{3}P_{\mathrm{0}}$) to Ga (4$p$ $^{2}P_{1/2}$) ground-state to ground-state transition, yielding a preliminary value for the Ga electron affinity. $s$-wave thresholds were also observed for detachment from the J $=$ 1 and J $=$ 2 excited levels of Ga$^{-}$, yielding preliminary values for the fine structure splittings. The values measured in the present work are compared with previous results [1, 2].\\[4pt] [1] W. W. Williams \textit{et al}., J. Phys. B \textbf{31}, L341 (1998);\\[0pt] [2] T. Andersen \textit{et al.}, J. Phys. Chem. Ref. Data \textbf{28}, No. 6, 1511 (1999). [Preview Abstract] |
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Q1.00088: Inner-shell Photoionization of Atomic Chlorine: Experiment and Theory W.C. Stolte, Z. Felfli, A.Z. Msezane, R. Guillemin, G. Ohrwall, S.-W. Yu, J.A. Young, D.W. Lindle, T.W. Gorczyca, N.C. Deb, A. Hibbert, S.T. Manson Relative partial cross sections have been measured following photoabsorption by atomic chlorine in the vicinity of the Cl 2$p$ and 1$s $ionization thresholds including the charge state fractions of the residual Cl ions. In addition, Breit-Pauli R-Matrix calculations have been performed in the vicinity of the 2$p$ thresholds which show reasonably good agreement with experiment. Including spin-orbit interactions, there are ten 2$p^{5}$3$s^{2}$3$p^{5}$ thresholds of Cl$^{+}$, and a total of 64 resonance series leading up to these thresholds from the ground J$=$3/2 state of the Cl atom; the results show two groups of resonances, broad in connection with the higher-energy thresholds, and narrow for the lower-energy Cl$^{+}$ thresholds. This is explained in terms of the angular momentum geometry of the situation which demonstrates that the wide transitions can decay \textit{via} the monopole term in the expansion of the inter-electron Coulomb interaction, while for the narrow resonances, the leading term is the (significantly smaller) dipole term. In the vicinity of the 1$s $thresholds, the 1$s \to $3$p$ resonance is seen clearly; otherwise the spectrum is quite similar to Ar. [Preview Abstract] |
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Q1.00089: 3D Imaging the Photoionization of Propane at the Carbon K-Edge A. Gatton, J.B. Williams, T. Jahnke, M.S. Sch\"{o}ffler, R. D\"{o}rner, Th. Weber, A.L. Landers We have used Cold Target Recoil Ion Momentum Spectroscopy (COLTRIMS) to investigate the Carbon K-shell photoionization of Propane ($C_{3}H_{8}$) by 295eV photons and the subsequent auger decay leading to molecular dissociation. We present preliminary data analysis including calibration and identification of dissociation channels. Identified channels that may yield Molecular Frame Photoelectron Angular Distributions (MFPADS) or dynamical information include: \begin{eqnarray} \gamma_{295eV} + C_{3}H_{8} &\Rightarrow& e_{photo} + e_{auger} + H^{+} + C_{3}H_{7}^{+} \nonumber \\ \gamma_{295eV} + C_{3}H_{8} &\Rightarrow& e_{photo} + e_{auger} + CH_{3}^{+} + C_{2}H_{5}^{+} \nonumber \\ \gamma_{295eV} + C_{3}H_{8} &\Rightarrow& e_{photo} + e_{auger} + CH_{3}^{+} + CH_{3}^{+} + CH_{2}. \nonumber \end{eqnarray} Analysis is underway to determine the body frame of the molecule and to investigate the influence of the molecular potential and dissociation pathways on the photoelectron emission. [Preview Abstract] |
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Q1.00090: Solution Phase Molecular Dynamics Probed with Synchrotron Hard X-rays Anne Marie March, Gilles Doumy, Elliot P. Kanter, Stephen H. Southworth, Linda Young, Zoltan Nemeth, Gyorgy Vank\'o, Tadesse Assefa, Wojciech Gawelda The ability to measure short-lived transient states during a chemical reaction is key to understanding many important processes such as oxygen binding in hemeproteins and electron transport in photosynthesis. Time resolved hard x-ray spectroscopies, which are based on laser-pump/x-ray-probe methods, are a unique tool because unlike UV-VIS techniques they are element specific and can provide electronic and structural information with atomic resolution in the vicinity of a particular atom or ion. These characteristics make them particularly powerful for studying molecules in complex environments such as solutions. Using a MHz, picosecond, high average power laser system implemented at Sector 7ID-D of the Advanced Photon Source [1] we have been developing time resolved x-ray emission techniques to track the evolution of photoexcited molecules in solution. We will present recent studies which include the ligand substitution reaction and hydrated electron formation in the coordination complex ferrocyanide Fe(CN)$_{6}^{4-}$.\\[0pt] [1] A. M. March {\it et al.}, RSI, {\bf 82}, 073110 (2011). [Preview Abstract] |
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Q1.00091: Electron interference effects in energetic photoelectrons from C$_{60}$@C$_{240}$ probed by the Fourier spectroscopy Meghan McCreary, Himadri Chakraborty The ground state structure of the simplest two-fullerene onion system, the C$_{60}$@C$_{240}$ molecule, is solved in the Kohn-Sham framework of local density approximation (LDA). Calculations are carried out with delocalized carbon valence electrons after modeling the onion ion-core of sixty C$^{4+}$ ions from C$_{60}$ and two hundred and forty of those from C$_{240}$ in a smeared out jellium-type double-shell structure [1,2]. Ionization cross sections of all the levels are then calculated in both independent particle LDA and many-particle time dependent LDA approaches at photon energies above the plasmon resonances. These high-energy results exhibit rich structures of energy dependent oscillations from the quantum interference of electron waves produced at the edges of the fullerene layers. A detailed scrutiny of these structures is conducted by Fourier transforming the spectra to the configuration space [3] that relates the oscillations to the onion geometry.\\[4pt] [1] M.E. Madjet, H.S. Chakraborty, J.-M. Rost, and S.T. Manson, \textit{J. Phys.} B \textbf{41}, 105101 (2008);\\[0pt] [2] M.A. McCune, R. De, M.E. Madjet, H.S. Chakraborty, and S.T. Manson, \textit{J. Phys.} B Fast Track Comm. \textbf{44}, 241002 (2011); [3] M.A. McCune, M.E. Madjet, and H.S. Chakraborty, \textit{Phys. Rev.} A \textbf{80}, 011201 (R) (2009). [Preview Abstract] |
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Q1.00092: Channel asymmetry in the dissociation of HD$^{+}$ using an intense ultrafast single color laser field M. Zohrabi, B. Rigsbee, U. Ablikim, K.D. Carnes, B.D. Esry, I. Ben-Itzhak We have studied laser-induced fragmentation of molecular-ion beams using a coincidence 3D momentum imaging technique, which affords us the ability to measure both neutral and ionic fragments. These measurements provide detailed kinetic energy release (KER) and angular distributions of the different fragmentation processes. We focus mainly on the simplest heteronuclear molecule, HD$^+$, (using 25-65 fs laser pulses) as a model for more complex systems. We use deuterium tagging to distinguish different final products and thus study how to control one outcome over another. The preference for HD$^+$ to dissociate into either H$^+$+ D or H + D$^+$ is a good example of this kind of control - usually referred to as controlling the branching ratio. One would expect the H$^+$+ D channel, associated with the HD$^+$ electronic ground state, to dominate over dissociation into H + D$^+$ for very slow fragmentation. Our measured branching ratio confirms this prediction, but it also exhibits differences between these two channels in the higher KER region (0.5-1.2 eV). Furthermore, theoretical calculations show similar features in both KER regions. [Preview Abstract] |
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Q1.00093: Photoemission of Cooper Pairs from Aromatic Hydrocarbons Tim Hartman, Pavle Jurani\'c, Kelly Collins, Bethany Reilly, Emily Makoutz, Scott B. Whitfield, Narayan Appathurai, Ralf Wehlitz We have measured the ratio of doubly to singly charged molecular parent ions of benzene, naphthalene, anthracene, coronene, pyrrole, and furan over a wide range of photon energies. About 40 eV above the double-ionization threshold, the first four of the above molecules exhibit a hump of very similar shape and magnitude in the double-to-single photoionization ratio, which we attribute to the formation and emission of an electron Cooper pair from a free molecule.\footnote{R.\ Wehlitz {\it et al.} Phys.\ Rev.\ Lett. \textbf{109}, 193001 (2012)} Our results suggest that the de Broglie wave of this highly correlated pair of electrons forms a closed loop in the system of overlapping $\pi$ bonds with a wavelength that matches the distance between neighboring carbon atoms. Interestingly, coronene also exhibits a hump that corresponds to a de Broglie wavelength of twice the C--C distance. Pyrrole and furan, on the other hand, do not show any hump in the ratio probably due to their pentagonal structure. Photoelectron measurements indicate the break-up of the emitted Cooper pair in support of our interpretation. [Preview Abstract] |
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Q1.00094: Optimal wavelength for carrier-envelope phase effects in $\rm{H}_2^+$ Shuo Zeng, Brett Esry We have solved the time-dependent Schr\"odinger equation for the benchmark molecule H$_2^+$ in intense, few-cycle laser pulses over a broad wavelength range from 800~nm to 2000~nm. We extract the momentum distribution of the $p$+H fragments following dissociation, focusing on the carrier-envelope phase (CEP) effects. The calculations include all degrees of freedom but neglect ionization. We interpret the wavelength dependence of the CEP effects using our previously developed Fourier-Floquet framework [1,2]. We find that longer wavelengths yield stronger CEP control and that there is a range of wavelengths that produce a relatively intensity-independent asymmetry pattern. This feature ensures that more of the CEP effects will survive the focal volume averaging over the laser intensity profile that is largely unavoidable in experiments. Different cuts through the laser parameter space will be used to highlight different aspects of the physics. \\[4pt] [1] V. Roudnev and B. D. Esry, Phys. Rev. Lett. 99, 220406 (2007)\\[0pt] [2] J. J. Hua and B. D. Esry, J. Phys. B 42, 085601 (2009) [Preview Abstract] |
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Q1.00095: High-quality multi-GeV electron beams from auto-resonance laser-acceleration Yousef Salamin, Benjamin Galow, Jianxing Li, Zoltan Harman, Christoph Keitel Results from many-particle simulations will be presented that demonstrate feasibility of generating an electron bunch of over 10-GeV energy and ultra-high quality (relative energy spread $\sim$ 10$^{-4})$ by cyclotron auto-resonance. The scheme employs a static magnetic field oriented along the direction of propagation of a laser beam. Tremendous energy gain by the electron from the laser field occurs if the injection conditions and laser and magnetic field parameters conspire to achieve auto-resonance: when the cyclotron frequency of the electron around the lines of the magnetic field match the Doppler-shifted frequency of the laser as seen by the electron. Accelerated electron bunches of the above-mentioned characteristics are suitable for fundamental high-energy particle physics research. In our calculations, the laser peak intensities and axial magnetic field strengths required are up to about 10$^{18}$ W/cm$^{2}$ and 60 T, respectively. Gains exceeding 100 GeV are shown to be possible when weakly focused pulses from a 200-PW future laser facility are used.\\[4pt] Reference: \textit{High-quality multi-GeV electron bunches via cyclotron autoresonance}, B. J. Galow, J.-X. Li, Y. I. Salamin, Z. Harman, and C. H. Keitel (submitted). [Preview Abstract] |
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Q1.00096: Attosecond relative time delays in streaked photoemission from Mg (0001) surfaces Q. Liao, U. Thumm We analyze attosecond relative time delays in the photoemission from conduction band (CB) and core levels (CL) of metal surfaces within a quantum-mechanical model. The relative delay between CB and CL photoelectrons is found to be sensitive to the electron mean free path and the screening of the NIR streaking field inside the solid. Our numerical results reproduce a recent attosecond-streaking experiment with an Mg(0001) surface [S. Neppl \textit{et al}., Phys. Rev. Lett. \textbf{109}, 087401 (2012)], which reveals no relative streaking time delay between CB and CL electrons. [Preview Abstract] |
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Q1.00097: Atomistic Computational Model of Ultrafast Response of Complex Systems in Intense X-rays Phay Ho, Wei Jiang, Linda Young We present a combined Monte-Carlo/Molecular-dynamics (MC/MD) computational model for treating ultrafast electronic damage processes and the subsequent structural distortion on complex systems exposed to femtosecond, high-intensity x-ray free-electrons laser pulses. ~Our first target systems are nickel nanoparticles since the range for self-seeded LCLS operation (7.1-9.5 keV) spans the nickel K-edge (8333 keV). Our MC/MD method includes the contribution of photoelectrons, Auger electrons, fluorescence photons and secondary electrons. ~It goes beyond the earlier particle approaches by tracking the electronic configuration of each charged particle throughout the x-ray pulse. With this new capability, we present the impact of both transient core-hole states and delocalized electrons, which may exist within, or within the proximity, of the nanoparticle, on the measured coherent x-ray diffraction pattern. [Preview Abstract] |
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Q1.00098: Sulfur-doped microstructures formed in silicon using a modulated continuous wave laser R. Ayachitula, L. Brandt, M. Chilton, R.J. Knize, B.M. Patterson We demonstrate the enhanced optical properties of silicon microstructures formed by irradiation of a silicon surface by a modulated continuous wave (CW) laser beam in the presence of SF$_{6}$. The microstructures are doped with about 0.6{\%} sulfur, which extends the absorption well below the 1.1$\mu$m bandgap of crystalline silicon and results in a 60{\%} increase in the absorption of infrared radiation. This enhanced absorption as a result of these microstructures has been studied over the past decade in an effort to create high responsivity detectors and night vision goggles and improve the efficiency of solar cells. The enhanced optical absorption data we demonstrate are comparable to observations made in previous studies which were performed using more expensive and complicated laser systems such as regeneratively-amplified femtosecond pulsed laser systems and nanosecond and picosecond pulsed excimer lasers. [Preview Abstract] |
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Q1.00099: Optimizing High Harmonic Generation for X-ray Free Electron Laser Seeding Elio Champenois, James Cryan, Rafal Rakowski, Ali Belkacem, Roger Falcone As the next generation of free electron lasers~(FELs) are being designed and built, one problem that is being addressed is that of the temporal and spectral instabilities inherent to an initially spontaneous process. High harmonic generation~(HHG) has emerged as a means to generate vacuum and extreme ultraviolet~(VUV, EUV) photon fluxes high enough to overcome spontaneous noise, making it a candidate for seeding of FELs. We are developing an HHG beamline that maximizes the absolute photon flux in the 30--60~eV range where a high gain harmonic generation FEL could be seeded. The HHG drive laser for our source operates at 1~kHz, with $\sim$30~mJ pulses compressed to 27~fs and loosely focused into a gas cell. We investigate the effects of shaping the driving electric field on the HHG process. We discuss the challenges associated with this high average power setup and our current results from optimizing harmonic yield. [Preview Abstract] |
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Q1.00100: Valence shell photoionization of SF$_{6}$ and high harmonic generation Jobin Jobin, K. Fulfer, B. Wilson, E. Poliakoff, C. Trallero, S. Mondal, A.-T. Le, C.-D. Lin, Robert Lucchese When an atom or molecule is exposed to highly intense laser fields, the target can emit coherent radiation at photon energies which are multiples of incident laser energy. This process is known as High-order harmonic generation (HHG). There has been experimental and theoretical investigation of HHG for atoms and simple linear molecules. However, there have been few such studies for non-linear polyatomic molecules. In the current work, we investigate HHG for SF$_{6}$ experimentally and theoretically. We employ quantitative rescattering theory (QRS) which makes use of the magnitude and phase of the dipole transition matrix elements for photoionization. For calculating dipole transition matrix elements we employ the ePolyscat static-exchange method. The features seen in the computed results will be compared to corresponding features in the measured HHG spectrum. The calculation is repeated for different polarization of incident laser and different intensities. The analysis allows us to reproduce then understand experimentally measured HHG spectra from SF$_{6}$. Additionally, the valence shell photoionization parameters are also compared with several other theoretical and experimental results. [Preview Abstract] |
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Q1.00101: Phase diagram of Rydberg atoms in a nonequilibrium optical lattice Jing Qian, Guangjiong Dong, Lu Zhou, Weiping Zhang We study the quantum nonequilibrium dynamics of ultra-cold three-level atoms trapped in an optical lattice, which are excited to their Rydberg states via a two-photon excitation with non-negligible spontaneous emission. Rich quantum phases, including the uniform phase, the antiferromagnetic phase, and the oscillatory phase are identified. We map out the phase diagram and find these phases can be controlled by adjusting the ratio of intensity of the pump light to the control light and that of two-photon detuning to the Rydberg interaction strength. When the two-photon detuning is blueshifted and the latter ratio is less than 1, bistability exists among the phases. Actually, this ratio controls the Rydberg-blockade and Rydberg-antiblockade effects, thus, the phase transition in this system can be considered as a possible approach to study both effects. [Preview Abstract] |
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Q1.00102: Calculation of the ionization energy change due to neighboring charges occurring in laser-cluster interactions Edward Ackad, Jeff White Single-photon ionization is the initial mechanism by which a nanoplasma is formed during laser-cluster interactions in the VUV and beyond. While the photo-ionization cross-sections for gasses are well known, how to treat the ionization in charged, rare-gas clusters remains an open question. Using DFT, we model the effect of a cluster background field on an atom, solving for the ionization energy of the quantum system. We then propose a simple, semi-classical model which may be used in practice for large scale laser-cluster hybrid simulations. [Preview Abstract] |
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Q1.00103: Exciting and probing polarized strontium Rydberg atoms Moritz Hiller, Shuhei Yoshida, Joachim Burgdoerfer, Shuzhen Ye, Xinyue Zhang, F. Barry Dunning Today, Rydberg wave packets in effective one-electron systems can be engineered with high precision. However, the same manipulation schemes are considerably harder to realize in many-electron systems. A typical starting point for the control protocols is an optically accessible state such as a low-$\ell $ state or a polarized Stark state. Here, we examine the photoexcitation of strontium Rydberg states in an applied dc field and examine their polarization for this two-electron system. In strontium the ``$n$d'' states possess high two-photon excitation rates, display a large quantum defect, and are well isolated from their neighboring Stark manifolds. With increasing dc field, the ``$n$d'' states mix with this manifold of highly-polarized states. Initially the ``$n$d'' states suffer only a very small Stark shift, indicating their weak polarization. However, in fields approaching the $n$-mixing regime, sizable shifts are seen pointing to strong mixing and creation of strongly-polarized states. A very sensitive probe of their polarization is described which can detect even the weak polarization induced in small dc fields. [Preview Abstract] |
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Q1.00104: Precision polarizability measurements of atomic cesium's $8s \, ^2 \! S_{1/2}$ and $9s \, ^2 \! S_{1/2}$ states Hannah Weaver, Andrew Kortyna We report hyperfine-resolved scalar polarizabilities for cesium's $8s\,^2\!S_{1/2}$ and $9s\,^2\!S_{1/2}$ states using resonant two-photon spectroscopy. Two single-mode, external-cavity diode lasers drive the $6s\,^2\!S_{1/2}\rightarrow 6p\,^2\!P_{1/2}\rightarrow ns\,^2\!S_{1/2}$ transition ($n=8$ or 9). Both laser beams are split and counter-propagate through an effusive beam and a vapor cell. An electric field applied across two parallel plates imposes Stark shifts on the $ns\,^2\!S_{1/2}$ levels in the effusive beam. Electric-field strengths are measured {\em in situ}. The laser frequency is calibrated in the vapor cell using a phase modulation technique, with the modulation frequency referenced to the ground-state hyperfine splitting of atomic rubidium. Our measured $8s\,^2\!S_{1/2}$ polarizability, $38370\pm 380 a_0^3$, agrees with previous theory and experiments. Our measured $9s\,^2\!S_{1/2}$ polarizability, $150700\pm 1100 a_0^3$, agrees within two sigma of theory, but we are unaware of previous measurements. We also verify that these polarizabilities are independent of the hyperfine levels, placing upper limits on the differential polarizabilities of $200\pm 260 a_0^3$ for the $8s\,^2\!S_{1/2}$ state and $490\pm 450 a_0^3$ for the $9s\,^2\!S_{1/2}$ state. [Preview Abstract] |
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Q1.00105: Development of the relativistic all-order method for the calculation of isotope shifts Z. Zuhrianda, M.S. Safronova The comparison of the experimental and theoretical values of isotope shifts allows to determine the changes in the nuclear radius between two isotopes which are needed for many applications. Precision knowledge of isotope shifts is also needed for astrophysical search for the variation of the fine-structure constant. The specific mass shift (SMS) is extremely difficult to accurately calculate even for Na owing to large high-order correlation corrections. In fact, the calculations of the SMS constants in K and Rb carried out using two of the most accurate known methods for calculation of alkali properties were shown recently to disagree severely with each other and with experiment [Dzuba et al., PRA 72, 22503 (2005)]. In this work, we develop a relativistic all-order method for the evaluation of the specific mass shift by explicitly calculating SMS as the expectation value of corresponding one- and two-particle operators within the framework of all-order method. Combining this method with previously developed all-order method for the calculation of the field shift [Safronova et al., PRA 64, 052501 (2001)], we evaluate the isotope shifts in monovalent systems. [Preview Abstract] |
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Q1.00106: ATOMIC, MOLECULAR, AND CHARGED PARTICLE COLLISIONS III |
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Q1.00107: VUV Study of Electron-Pyrimidine Dissociative Excitation Jeff Hein, Hajar Al-Khazraji, Collin Tiessen, Dragan Lukic, Joshuah Trocchi, William McConkey A crossed electron-gas beam system coupled to a VUV spectrometer has been used to investigate the dissociation of pyrimidine (C$_{4}$H$_{4}$N$_{2})$ into excited atomic fragments in the electron-impact energy range from threshold to 375 eV. Data have been made absolute using Lyman-$\alpha $ from H$_{2}$ as a secondary standard. The main features in the spectrum are the H Lyman series lines. The emission cross section of Lyman-$\alpha $ is measured to be (2.44 $\pm$ 0.25) 10$^{-18}$ cm$^{2}$ at 100 eV impact energy. The probability of extracting C or N atoms from the ring is shown to be very small. Possible dissociation channels and excitation mechanisms in the parent molecule will be discussed. [Preview Abstract] |
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Q1.00108: Formation of negative ions in the interstellar medium by dissociative electron attachment to the H$_2$CN molecule Viatcheslav Kokoouline, Samantha Fonseca dos Santos, Nicolas Douguet, Ann E. Orel The methylene amidogen radical (H$_2$CN) was first discovered, in 1962 by Cochran $et\ al.$ [1], and since then it has received considerable attention from both experimentalists and theoreticians. It is considered an important intermediate in the combustion of nitramine propellants and proposed to play a role in extraterrestrial atmospheres. It was detected in interstellar clouds in 1994 [2], and its dissociative electron attachment (DEA) process may be responsible for the formation of the CN$^-$ and the H$^-$ negative ions: $e^-$+H$_2$CN $\to$ CN$^-$ + H$_2$; $e^-$+H$_2$CN $\to$ H$^-$ + HCN. We report here the results of our ab initio quantum chemical studies of the geometrical and electronic structure of the methylene amidogen and and its negative ion H$_2$CN$^-$ in the theoretical of DEA in H$_2$CN. The scattering calculations are carried out using the complex Kohn variational method. The nuclear dynamics, including dissociation, will later be treated using the MCTDH code [3] with a three-dimensional potential energy surface, in which the distance of CN is kept frozen. [1] E. L. Cochran $et\ al.$ J. Chem. Phys., 1962, 36, 1938. [2] M. Ohishi $et\ al.$, Astrophys. J., 1994, 427, L51. [3] G. A. Worth $et\ al.$, MCTDH package, Version 8.4 [Preview Abstract] |
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Q1.00109: Search for Asymmetric Interactions between Chiral Molecules and Spin-Polarized Electrons Joan Dreiling, Eric Litaker, Timothy Gay We present our preliminary asymmetry results for the transmission of longitudinally spin-polarized electrons through a vapor of chirally-pure bromocamphor (C$_{10}$H$_{15}$BrO) molecules. We define the asymmetry for transmission as A $=$ [(I$\uparrow $-I$\downarrow )$/(I$\uparrow +$I$\downarrow )$]$_{R\, }$- [(I$\uparrow $-I$\downarrow )$/(I$\uparrow +$I$\downarrow )$]$_{L}$, where I$\uparrow $ (I$\downarrow )$ is the transmitted current measured for spin-up (spin-down) electrons and the ``L'' and ``R'' subscripts correspond to the left- and right-handed chirality of the molecules. At present, we have measured A at 1.5 eV electron scattering energy to be 5.4(2.5)*10$^{-5}$ when the transmitted, magnetically collimated electron beam is attenuated to 10{\%} of its initial value, corresponding to a pressure of a few millitorr in a cell of length 2.54 cm. This should be compared with the measurements of Mayer et al., where they report an asymmetry (by our definition) of about 3.4(0.2)*10$^{-4}$ for the same incident energy and electron beam attenuation [1]. We discuss possible reasons for this discrepancy. \\[4pt] [1] S. Mayer, C. Nolting, and J. Kessler, J. Phys. B 29, 3497 (1996). [Preview Abstract] |
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Q1.00110: O($^1$D) Production in Electron-Carbon Dioxide Collisions Wladek Kedzierski, Jeff Hein, Collin Tiessen, Dragan Lukic, Joshuah Trocchi, Tim Mlinaric, William McConkey O($^1$D) is an important species in the earth's atmosphere giving rise to the well known oxygen red lines at wavelengths of 630.0 and 636.4 nm from the upper atmosphere and strongly influencing stratospheric photochemistry. O($^1$D) is metastable and is difficult to detect selectively in the laboratory. Using techniques and instrumentation developed in our laboratory we have studied the excitation of O($^1$D) following dissociative excitation of CO$_2$ in the electron impact energy range from threshold to 300 eV. A solid Ne matrix at 10K forms the heart of the detector. This is sensitive to the metastable species through the formation of excited excimers (NeO*) which immediately radiate. Using a pulsed electron beam and time-of-flight techniques we have measured relative cross sections as a function of impact electron energy. Threshold energy data are used to gain information about the parent molecular states. [Preview Abstract] |
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Q1.00111: Near-Threshold Electron Impact Excitation of Molecular Nitrogen Charles P. Malone, Paul V. Johnson, Jeffrey D. Hein, Brandon Grisanti, Murtadha A. Khakoo We present electron energy-loss (EEL) derived excitation cross sections for near-threshold electron impact of N$_{2}$. Differential cross sections (DCSs) and integral cross sections (ICSs) were obtained by unfolding EEL spectra in the $\sim6-11$eV range for the $\it{A}$ $^{3}\Sigma_{\it{u}}^{+}$, $\it{B}$ $^{3}\Pi_{\it{g}}$, $\it{W}$ $^{3}\Delta_{\it{u}}$, $\it{B}^{\prime}$ $^{3}\Sigma_{\it{u}}^{-}$, $\it{a}^{\prime}$ $^{1}\Sigma_{\it{u}}^{-}$, $\it{a}$ $^{1}\Pi_{\it{g}}$, and $\it{w}$ $^{1}\Delta_{\it{u}}$ electronic states over the $\sim0-130^{\circ}$ scattering angular range. Vibrationally-resolved DCSs and ICSs were obtained for stronger vibronic transitions, including the $\it{a}$ $^{1}\Pi_{\it{g}}$ state, which generates the atmospherically important Lyman-Birge-Hopfield (LBH) emissions. The summed near-threshold excitation cross sections ($\it{A}$+$...$+$\it{w}$) generally are larger than previous measurements. [Preview Abstract] |
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Q1.00112: Disscociative Recombination of N$_2$H$^+$ Samantha Fonseca dos Santos, Nicolas Douguet, Viatcheslav Kokoouline, Ann Orel, Asa Larson N$_2$H$^+$ is among the first molecular ions observed in the ISM. It is formed by fast proton transfer mechanisms and destroyed either by taking part on the molecular synthesis of more complex molecules or by dissociative recombination (DR). We will present theoretical results on the dissociative recombination (DR) of N$_2$H$^+$ at electronic impact energies ranging from 10$^{-3}$ to 8 eV. At low energies, the main contribution to DR comes from the indirect DR process and the calculation have been made within the framework of a simplified model based on multi-channel quantum defect theory. For energies above 0.1 eV, the main DR process is the direct DR and the dissociation dynamics was treated in a time-dependent picture using the MCTDH package. We calculated cross sections and DR rates, and compared with the available experimental data from the CRYRING storage ring experiment. [Preview Abstract] |
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Q1.00113: Radiative electronic attachment to a ro-vibrating diatomic molecule: Benchmark study of CN$^-$ Nicolas Douguet, Viatcheslav Kokoouline, Samantha Fonseca dos Santos, Olivier Dulieu, Maurice Raoult, Ann Orel We study the process of radiative electronic attachment (REA) to linear molecules of astrophysical interest and consider in detail the reaction CN+e$^-\to$CN$^-$+$\hbar\omega$. The treatment is based on first-principles only and takes into account the rotational and vibrational motion of the diatomic molecule. The energy-dependent transition dipole moment between the continuum and bond electron is obtained for various molecular geometries using the complex Kohn variational method. The benchmark calculation for the formation of CN$^-$ by REA has produced a low rate coefficient of about $10^{-15}$cm$^3/$s at 30 K. This confirms the idea that the simplest observed negative ion CN$^-$ can not be formed by the process of radiative electron attachment. Note that the same type of treatment could be equivalently used to study photodetachment of a ro-vibrating linear negative ion. [Preview Abstract] |
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Q1.00114: PTCDA in Helium Nanodroplets: Doping Characterizationand Spectroscopic Investigations with a Pulsed Helium Nanodroplet Beam Aaron LaForge, Markus Mueller, Frank Stienkemeier Organic semiconductors like PTCDA have gained considerable interest because of their optoelectronic properties. To reveal electronic structures we utilize Helium Nanodroplet Isolation (HENDI) Spectroscopy as well established method to characterize single molecules, but also molecular complexes inside a cold (370mK) and weak interacting environment. We present PTCDA doping characteristics for a pulsed helium nanodroplet beam either measured by Laser Induced Fluorescence (LIF) or by Quadrupole Mass Spectrometry (QMS). The comparison between time resolved LIF and QMS intensities gives information about the doping within one helium nanodroplet pulse. Furthermore, spectroscopic results from LIF excitation and fluorescence emission measurements for single PTCDA molecules attached to helium nanodroplets give insight into the vibrational structure of the electronic ground state and the first electronically excited state. [Preview Abstract] |
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Q1.00115: Hydrogen anion formation by electron capture in collisions of hydrogen atoms with an Al(100) surface B. Obreshkov, U. Thumm We theoretically investigate the electron transfer dynamics during the reflection of hydrogen atoms on an Al(100) surface for a wide range of collision energies below 6 $\sim$ keV. We find a non-monotonic variation of the hydrogen-negative-ion fractions as functions of the projectile impact velocity due to non-adiabatic electron transfer. Our calculated anion fractions for projectiles scattered along high Miller-index crystal-surface directions [1] are in good quantitative agreement with measured hydrogen anion fractions [2] for a wide range of exit velocities. \\[4pt] [1] B. Obreshkov and U. Thumm, Phys. Rev. A \textbf{83} 062902 (2011) and to be published.\\[0pt] [2] M. Maazouz, R. Baragiola, A. Borisov, V. A. Esaulov, S. Lacombe, J. P. Gauyacq, L. Guillemot, and D. Teillet-Billy, Surf. Sci. \textbf{364}, 568 (1996). [Preview Abstract] |
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Q1.00116: Controlling ultracold chemical reactions via Rydberg-dressed interactions Jia Wang, Jason Byrd, Ion Simbotin, Robin C\^{o}t\'{e} Chemical reactions in the cold and ultracold temperature regimes are sensitive to the long-range interaction between reactants. This is especially the case when there is a weakly bound state near the collision threshold. Altering the long-range potential provides a tool to control the chemical reaction by shifting the position of near threshold bound states. In this work, we study the effect of Rydberg-dressing a reactant, which can be accomplished experimentally by weakly coupling its ground state to a Rydberg state using a strongly detuned laser. This leads to an enhancement in the effective polarizability of the reactant and hence a modification of the long-range interaction. We theoretically investigate this effect in the benchmark system H$_2$+D, and carry out a full quantum mechanical scattering calculation for the reaction rates. [Preview Abstract] |
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Q1.00117: Electron-like scattering of positronium with Helium Joseph Di Rienzi, Richard Drachman A recent work [1] established experimentally that positronium (Ps) scattering by various atoms is close in total cross-section to that of an isolated electron of the same velocity. This presumes that the e- in Ps moves very similar to a free e- scattering off an element such as He, and that the positron has little contribution. Most theoretical models of Ps scattering through He have considered the excitation of Ps the dominant effect. Yet, these do not show much difference in the scattering length from a static exchange formulation [2] even with many Ps states [3]. In this work we will examine two different models of Ps-He scattering. First, we look at electron exchange with some excited states of He using a variational method, and then at exchange with excited states of Ps. Finally, we compare the two scattering results determined to see if a target-inelastic model has a greater effect than a projectile-inelastic model.\\[4pt] [1] S. J. Bromley, S. Armitage, J. Beale, D. E. Leslie, A. I. Williams, G. Laricchia, Science 330, 789 (2010).\\[0pt] [2] P.A. Fraser and M. Kraidy. Proc. Phys. Soc., 89, 533 (1966); M. Kraidy. private communication (1969).\\[0pt] [3] J.E. Blackwood, C. P. Campbell, M. T. McAlinden and H. R. J. Walters. Phys. Rev. A, 60, 4454 (1999). [Preview Abstract] |
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Q1.00118: ATOMIC AND MOLECULAR STRUCTURE, INCLUDING IN STATIC FIELDS |
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Q1.00119: The role of vibrational dynamics in resonant positron annihilation on molecules A.C.L. Jones, M.R. Natisin, J.R. Danielson, C.M. Surko Vibrational Feshbach resonances (VFRs) are dominant features of positron annihilation for incident positron energies in the range of the molecular vibrations\footnote{G. F. Gribakin, J. A. Young, C. M. Surko, Rev. Mod. Phys. {\bf 82}, 2557 (2010).}. Recent discovery of a broad spectral component due to multimode VFRs\footnote{A. C. L. Jones \emph{et al.}, Phys. Rev. Lett. {\bf 108}, 093201 (2012).} has enabled more accurate investigation of the deviation of resonant amplitudes from the predictions of the VFR model. Studies in relatively small molecules are described that elucidate the role of intramolecular vibrational redistribution (IVR) into near-resonant multimode states, and the subsequent coupling of these modes to the positron continuum, in suppressing or enhancing these resonances. A simple rate model is presented that places limits on the enhancement and suppression of VFRs due to IVR. The implications for annihilation in other molecular species, and the necessary ingredients of a more complete theory of resonant positron annihilation, are discussed. [Preview Abstract] |
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Q1.00120: Cryogenic Positron Beams for Atomic Physics Experiments M.R. Natisin, J.R. Danielson, A.C.L. Jones, C.M. Surko Trapped positron plasmas are routinely used to generate positron beams that can be used for a wide variety of experiments. For example, positron attachment to molecules occurs via the excitation of vibrational Feshbach resonances, yielding large peaks in the annihilation rate. These rates are measured as a function of positron energy by passing a beam through a molecular gas. While current beam generation techniques are sufficient for the measurement of positron-molecule binding energies,\footnote{G. F. Gribakin, et al., {\it Rev. Mod. Phys.} {\bf 82}, 2557 (2010).} more detailed studies are limited by beam energy resolution. Described here is a new method of positron beam formation using a buffer gas cryogenically cooled to 50 K. Simulations of the beam formation process are discussed and used to predict an energy resolution of $\approx$ 9 meV FWHM; a factor of 5 improvement over current techniques. Various possible physical measurements using this technique are discussed, including the ability to resolve individual multimode features in the resonant spectra,\footnote{A. C. L. Jones et al., {\it Phys. Rev. Let.} {\bf 108}, 093201 (2010).} and more detailed studies of annihilation involving intramolecular vibrational energy redistribution (IVR). [Preview Abstract] |
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Q1.00121: Measuring positron-atom binding energies through laser-assisted photo-recombination C.M. Surko, J.R. Danielson, R.E. Continetti, G.F. Gribakin Trap-based positron beams are important for a range of atomic physics experiments. They have, for example, enabled the measurement of positron binding energies for over 60 molecules to date. However, in spite of numerous, accurate theoretical predictions, there have been no experiments to study positron attachment to atoms, due primarily to the difficulty of forming these attached states in two-body collisions. Described here is the proposal for an experiment to use laser-assisted photo-recombination (LAPR) of positrons and metal atoms in the vapor phase to study positron binding to atoms.\footnote{C. M. Surko, J. R. Danielson, G. F. Gribakin, and R. E. Continetti, {\it New J. Phys.} {\bf 14}, 065004 (2012).} This experiment relies on the development of a new hot-cell apparatus to provide a collision chamber for metal vapors. Signal rates are estimated for zinc atoms using $0.35$ eV photons. Important facets of the design of the experiment are based upon experience studying resonant annihilation spectra of molecules using a trapped based beam. [Preview Abstract] |
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Q1.00122: Variational calculations of low-energy elastic Ps-H scattering Denton Woods, S.J. Ward, P. Van Reeth Ps-H scattering is of interest, as it is a fundamental 4-body Coulomb problem, and measurements have been made of Ps scattering with atoms and molecules. We have computed accurate $^{1,3}S$ and $^{1,3}P$ phase shifts for elastic Ps-H scattering using the Kohn, inverse Kohn, generalized Kohn and complex Kohn variational methods [1-3]. We improved upon the numerics of the previous accurate Kohn and inverse Kohn variational calculations [4]. Using the quantum defect theory for the van der Waals interaction [5], we computed the $^1P$ and $^3P$ scattering lengths. We are in the process of computing the $^1D$-wave phase shifts [3].\\[4pt] [1] D. Woods, S. J. Ward and P. Van Reeth, Bull. Am. Phys. Soc. {\bf 56}, no. 5, p. 165 (2011).\\[0pt] [2] Denton Woods, S. J. Ward and P. Van Reeth, Bull. Am. Phys. Soc. {\bf 57}, no. 5, p. 200 (2012); talk at CAARI, Fort Worth, Texas, 2012.\\[0pt] [3] Denton Woods, S. J. Ward and P. Van Reeth, http://meetings.aps.org/Meeting/MAR13/Event/185547.\\[0pt] [4] P. Van Reeth and J. W. Humberston, J. Phys. B {\bf 36}, 1923 (2003); Nucl. Instrum. Methods B {\bf 221} 140 (2004).\\[0pt] [5] Bo Gao, Phys. Rev. A {\bf 58}, 4222 (1998). [Preview Abstract] |
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Q1.00123: Comparison of positron and electron binding to molecules J.R. Danielson, A.C.L. Jones, M.R. Natisin, C.M. Surko Positrons can attach to molecules via Feshbach resonances in which a vibrational mode absorbs the excess energy. Using a high-resolution positron beam, this process has been used to measure positron-molecule binding energies for many chemical species.\footnote{G. F. Gribakin, et al., {RMP} {\bf 82}, 2557 (2010).} Recent measurements have focused on molecules with large permanent dipole moments (i.e., $\mu > 2.5$ D), including aldehydes, ketones, and nitriles.\footnote{J. R. Danielson, et al., {PRA} {\bf 85}, 022709 (2012).} Positron binding to these molecules is compared to the analogous weakly bound electron-molecule states, commonly referred to as ``dipole-bound'' negative anions.\footnote{N.~I.~Hammer, et al., {JCP} {\bf 119}, 3650 (2003).} Positron binding energies are found to be one to two orders of magnitude larger than those of the analogous negative ions due to two effects: the orientation of the molecular dipole allows the positron to approach it more closely; and for positrons, lepton correlations (e.g., via polarizability) contribute more strongly.\footnote{J. R. Danielson, et. al, {PRL} {\bf 109}, 113201 (2012)} Comparisons to available calculations will be presented, as will comparisons to binding to molecules with $\mu\sim 0$ (e.g., polarizability bound states). [Preview Abstract] |
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Q1.00124: Correlation in time-dependent density functional theory studies of antiproton-helium collisions Matthew Baxter, Tom Kirchner Correlation effects are examined in the context of time-dependent density functional theory calculations of antiproton helium collisions. An approximation for the correlation potential as well as two models for the correlation integral ($I_{\mathrm{c}}$) are explored. While one of these models (frozen correlation (FCM)) is entirely new the other is appropriated from the world of laser-induced ionization (Wilken and Bauer (WB))~[1]. Total cross sections for both single and double ionization in the range 1--2000 keV are presented. These calculations make use of the basis generator method and incorporate microscopic response. While the FCM results provide little improvement over an independent electron model description the WB model agrees quite well with experimental results for both single and double ionization. Our results also lend credence to the belief that an appropriate approximation of $I_{\mathrm{c}}$ is more important in reproducing correlation effects than the correlation potential~[2].\\[4pt] [1]~F. Wilken and D. Bauer, Phys. Rev. Lett. \textbf{97}, 203001 (2006);\\[0pt] [2]~N. Henkel {\it et al.}, Phys. Rev. A \textbf{80}, 032704 (2009). [Preview Abstract] |
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Q1.00125: Not only Gravitational Lensing, but in general Medium Lensing Florentin Smarandache According to the General Theory of Relativity the gravity curves the spacetime and everything over there follows a curved path. The space being curved near massive cosmic bodies is just a metaphor, not a fact. We dough that gravity is only geometry. The deflection of light (\textbf{Gravitational Lensing}) near massive cosmic bodies is not due because of a ``curved space'', but because of the medium composition (medium that could be formed by waves, particles, plasma, dust, gaseous, fluids, solids, etc.), to the medium density, medium heterogeneity, and to the electromagnetic and gravitational fields contained in that medium that light passes through. This medium deviates the light direction, because of the interactions of photons with other particles. The space is not empty; it has various nebulae and fields and corpuscles, etc. Light bends not only because of the gravity but also because of the medium gradient and refraction index, similarly as light bends when it leaves or enters a liquid, a plastic, a glass, or a quartz. The inhomogeneous medium may act as an optical lens such that its refractive index varies in a fashion, alike the \textit{Gradient-Index Lens}. We talk about a \textbf{Medium Lensing}, which means that photons interact with other particles in the medium. For example, the interaction between a photon of electromagnetic radiation with a charged particle (let's say with a free electron), which is known as \textit{Compton Effect}, produces an increase in the photon's wavelength. In the \textit{Inverse Compton Effect} the low-energy photons gain energy because they were scattered by much-higher energy free electrons. [Preview Abstract] |
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Q1.00126: Fully differential cross sections for $\bar{p}$ + H collisions T.G. Lee, M.F. Ciappina, M.S. Pindzola, J. Colgan We present fully differential cross sections (FDCS) for the single ionization of hydrogen atoms by antiprotons~[1]. We use a time-dependent close-coupling approach to model the evolution of the electron wavefunction in the field of the incoming projectile for a range of impact parameters and for different impact energies~[2]. In addition, a Fourier transform approach is used to extract FDCS for a specific projectile momentum transfer value~[3]. This scheme allows us to incorporate information about the interaction of the two heavy nuclei (the so-called NN interaction) and to assess its influence in the FDCS. We compare our approach with convergent close coupling methods~[4].\\[4pt] [1] M.\ F.\ Ciappina, et al., J. Phys. B (in preparation) (2013). \newline [2] T.\ G.\ Lee, et al., J. Phys. B {\bf 45}, 045203 (2012). \newline [3] J.\ Colgan, et al., J. Phys. B {\bf 44}, 175205 (2011). \newline [4] I.\ Abdurakhmanov, et al. J. Phys. B {\bf 44}, 165203 (2011). [Preview Abstract] |
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Q1.00127: Surprises In Computed Lyapunov Exponents Across The Quantum-Classical Transition Arjendu Pattanayak, Peter Duggins, Kevin Hallman, Dustin Anderson, Arie Kapulkin We calculate quantum lyapunov exponents for identical noise quantum trajectories for the damped driven double-well Duffing oscillator across a range of parameters, specifically as a function of effective hbar (=beta) as well as the system damping parameter Gamma. We demonstrate the recovery of the classical Lyapunov exponent in the limit of beta to 0. In general Lyapunov exponents decrease (chaos decreases) as beta increases (as the system becomes more quantal). However, we identify the following surprises: (a) Regions of anomalous increase of chaos (Lyapunov exponents increasing with beta); (b) Regions of anomalous ``quantum-induced'' onset of chaos (Lyapunov exponent going from negative to positive with increasing beta); and (c) Regions of incomplete correspondence for values of Gamma where the classical system has windows of regularity embedded in a larger chaotic parameter regime. For these last regions, the classical results are not recovered for the smallest beta we can computationally access (beta =0.003). We discuss the meaning and consequences of these results, as well as prospects for experimental verification. [Preview Abstract] |
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Q1.00128: A method for describe the image of interference and diffraction Sheng Ming Zheng In the process of exploring essence of light, Newton initially agreed with the particle interpretation of light while Huygens supported the wave theory. These two doctrines had been disputed in Newton's time. Until today this dispute has been carrying on. Why one particle has two forms. For solve this question, I do some experiments discover that the moving photons produce gravitation, and know that the light wave phenomenon is produced by gravitation. Then I came up with a new method to draw images of multi-pinhole diffraction patterns and their interference fringes.: given the perpendicular line for the line which links the nearest two pinholes, the point of intersection of this vertical line is quite right the image become on the screen. The more detail see below website: https://www.lap-publishing.com/catalog/details/store/gb/book/978-3-8473-2658-8/mechanism-of-interaction-in-moving-matter [Preview Abstract] |
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Q1.00129: Electron cooling and accumulation of 4$\times$10$^9$ positrons in a system for longterm storage of antihydrogen atoms D.W. Fitzakerley, M.C. George, E.A. Hessels, C.H. Storry, M. Weel, D. Grzonka, W. Oelert, G. Gabrielse, W.S. Kolthammer, R. McConnell, P. Richerme, A. M\"ullers, J. Walz For antihydrogen ($\overline{\rm H}$) production, trapping and spectroscopic measurements, large numbers of positrons (e$^+$) and antiprotons are required. These antimatter particles are captured, cooled and manipulated in extremely-high vacuum within our Penning-Ioffe trap system to ensure long lifetimes before annihilation with background gas, as required for precision experiments with antimatter atoms. Our ATRAP collaboration has accumulated up to 4$\times 10^9$ positrons (e$^+$) in our Penning-Ioffe trap apparatus which can be maintained at a temperature of 1.2 K and at a pressure below 6$\times 10^{-17}$ Torr. Realizing this extremely low pressure is particularly challenging given that the Penning-Ioffe trap apparatus is continuously open to the room-temperature e$^+$ accumulator where Ne and N$_2$ gasses are used to slow and capture the e$^+$ that originate from radioactive decay of $^{22}$Na. This low temperature and vacuum pressure should allow for $\overline{\rm H}$ storage times of over 1 year, sufficient time for high-precision tests of antimatter gravity and of CPT invariance. [Preview Abstract] |
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Q1.00130: POST-DEADLINE ABSTRACTS |
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Q1.00131: The Cooper-like minimum in the HHG of N$_2$: A TDDFT study Xi Chu, Gerrit Groenenboom A minimum at $\sim$39 eV is observed in the high-harmonic-generation spectra of N2 for several laser intensities and frequencies. This minimum appears to be invariant for different molecular orientations. We reproduce this minimum for a set of laser parameters and orientations in time-dependent density-functional-theory calculations, which also render orientation-dependent maxima at 23-26 eV. Photon energies of these maxima overlap with ionization potentials of excited states observed in photoelectron spectra. Time profile analysis shows that these maxima are caused by resonance-enhanced multiphoton excitation. We propose a four-step mechanism, in which an additional excitation step is added to the well-accepted three-step model. Excitation to a linear combination of Rydberg states c$_4?~^1\Sigma_u^+$ and c$_3~^1\Pi_u$ gives rise to an orientation-invariant minimum analogous to the ``Cooper minimum" in argon. When the molecular axis is parallel to the polarization direction of the field, a radial node goes through the atomic centers, and hence the Cooper-like minimum coincides with the minimum predicted by a modified two-center interference model that considers the de-excitation of the ion and symmetry of the Rydberg orbital. [Preview Abstract] |
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Q1.00132: Energy dependent relative charge transfer cross sections of Cs$^{+}$+ Rb(5s, 5p) Hai Nguyen, Darren Getts, Xavier Flechard, Richard Bredy, Brett DePaola Magneto optical trap recoil ion momentum spectroscopy (MOTRIMS) is a well known technique with excellent resolution. Its uses have been demonstrated in various ion atoms collision experiments as well as in probing various target excitation schemes. Here MOTRIMS is used to perform energy-dependent kinematically complete experiments of charge exchange cross sections for various channels at various projectile energies between Cs$^{+}$ + $^{87}$Rb(5s, 5p). The experimental technique and data from this ion-atom collision charge exchange process are presented. [Preview Abstract] |
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Q1.00133: ABSTRACT WITHDRAWN |
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Q1.00134: Light propagation in non-linear and disordered photo-induced lattices Julien Armijo, Diego Guzman, Camilo Cantillano, Dany Lopez, Luis Morales, Sebastian Etcheverry, Rodrigo Vicencio We present the first experimental results of our new non-linear optics lab at Universidad de Chile. We use photorefractive SBN crystals to photoinduce lattices of various geometries (square, hexagonal, Kagome, disordered, etc.), using a 532nm cw laser and spatial light modulators in real and Fourier space. In regular lattices, linear propagation of a focussed probe wave results in typical discrete diffraction patterns, with intense outer lobes expanding ballistically. Beyond the first Brillouin zone and the Bragg-reflection planes, we observe propagation in the second band. For an intense probe beam, the propagation entails a focussing non-linearity which can overcome diffraction and we observe the formation of continuous as well as discrete solitons. A wide input beam, on the other hand gets destabilized by modulational instability. Finally, in disordered landscapes, we study the Anderson Localization of light waves in 2D. The disorder-induced localization is strongly affected by the correlation properties of the disorder, as well as the spectral content of the probe beam. [Preview Abstract] |
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Q1.00135: A Nuclear-Electronic Spin Gyro-Comagnetometer Geoffrey Renon, Nassim Zahzam, Yannick Bidel, Alexandre Bresson, Pierre-Jean Nacher We have started a project aiming to fully characterize a new generation of atomic gyroscope based on the detection of a nuclear spin orientation with an alkali magnetometer [1]. The key element of the device is a spherical gas cell heated at about 110$^{\circ}$C and shielded from parasite magnetic fields. This cell is filled with an alkali gas (Rb) with an electronic spin and a noble gas ($^{129}$Xe) with a nuclear spin. $^{129}$Xe is polarized by Spin Exchange Optical Pumping (SEOP). The magnetic field created by the nuclear magnetization is canceled with a homogeneous magnetic field, so that Rb atoms feel no magnetic field and evolve in a collisional regime (Spin Exchange Relaxation Free -- SERF) allowing the realization of an ultra sensitive in situ alkali magnetometer [2] which detects the nuclear spin dynamic and then gives us a rotation measurement of the system. Our project deals with the conception, realization and characterization of this atomic spin gyroscope very promising for applications requiring miniature sensors with high performances.\\[4pt] [1] T.W. Kornack, et al., ``Nuclear Spin Gyroscope Based on an Atomic Comagnetometer'', PRL, vol. 95, 230801, 2005.\\[0pt] [2] I.K. Kominis, et al., ``A subfemtotesla multichannel atomic magnetometer'', Nature, vol. 422, p. 596-599, 2003. [Preview Abstract] |
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Q1.00136: The Molecular Hubbard Hamiltonian: Field Regimes and Molecular Species Erman Bekaroglu, Michael Wall, Kenji Maeda, Lincoln Carr The molecular Hubbard Hamiltonian (MHH) naturally arises for ultracold polar alkali dimer molecules in optical lattices. We show that, unlike ultracold atoms, different molecules display different many-body phases due to intrinsic variances in molecular structure. We also demonstrate a wide variety of experimental controls on molecules via external fields, including applied static electric and magnetic fields, an AC microwave field, and the polarization and strength of optical lattice beams. We provide explicit numerical calculations of the parameters of the MHH, including tunneling and direct and exchange dipole-dipole interaction energies, for the molecules 6 Li133 Cs, 23Na40 K, 87 Rb133 Cs, 40 K87 Rb, and 6 Li23 Na in weak and strong applied electric fields. As case studies of many-body physics, we use infinite-size matrix product state (iMPS) methods to explore the quantum phase transitions from the superfluid phase to half-filled and third-filled crystalline phases in one dimension. [Preview Abstract] |
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Q1.00137: A model of N$_2$ extreme-ultraviolet photoabsorption and dissociation Alan Heays, Brenton Lewis, Stephen Gibson The nitrogen molecule is a long-studied and difficult problem in molecular spectroscopy, and many important details of its interaction with radiation remain unexplained. A principal problem of continuing interest concerns the resonant photoabsorption and resultant predissociation of N$_2$ when exposed to extreme-ultraviolet radiation. A model of the excited states of N$_2$ has been developed in order to quantify their interactions and reproduce photoabsorption and photodissociation cross sections between 100000 and 118500 cm$^{-1}$ (100 and 84 nm) . This solves the radial Schroedinger equation within a coupled-channels formulation for new diabatic potential-energy curves, homogeneous and heterogeneous state mixing, and electronic transition moments for the optically allowed transitions. The accidental predissociation of ${}^1\Pi_u$ states between $100000$ and 112500 cm$^{-1}$ has been quantitatively modelled by spin-orbit coupling these to a set of ${}^3\Pi_u$ and ${}^3\Sigma_u^+$ states which includes unbound members. Following reference to a large experimental database, the model is both accurate and comprehensive and may be used to simulate synthetic cross sections suitable for use in high-resolution photochemical models of atmospheric and astrophysical environments. [Preview Abstract] |
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Q1.00138: A slow source of molecules for high resolution spectroscopy Marina Quintero-P\'erez, Paul Jansen, Thomas E. Wall, Wim Ubachs, Hendrick L. Bethlem We present experiments on decelerating and trapping ammonia molecules using a combination of a Stark decelerator and a traveling wave decelerator. In the traveling wave decelerator a moving potential is created by a series of ring-shaped electrodes to which oscillating high voltages are applied. By lowering the frequency of the applied voltages, the molecules confined in the moving trap are decelerated and brought to a standstill. As the molecules are confined in a true 3D well, this new kind of deceleration has practically no losses, resulting in a great improvement on the usual Stark deceleration techniques. The necessary voltages are generated by amplifying the output of an arbitrary wave generator using fast HV-amplifiers, giving us great control over the trapped molecules. We illustrate this by experiments in which we adiabatically cool trapped NH3 and ND3 molecules and resonantly excite their motion. Our main motivation for this research is the possibility to use the traveling wave decelerator as a source of cold molecules for a molecular fountain. Previous attempts to create a fountain using a Stark decelerator were unsuccessful due to losses at low velocities and a complex lens-system for cooling and collimating the slow beam. A traveling wave decelerator should solve both of these issues. [Preview Abstract] |
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Q1.00139: Quantal determination of the mobility of ground and excited C$^{+}$ ions evolving in a cooled helium gas Moncef Bouledroua, Lamia Aissaoui, Kamel Alioua We propose in this work to look at the mobility of C$^{+}$ ions moving in a neutral helium gas. The calculations are performed for the cooled buffer gas into three steps. The first step consists of calculating the interaction potentials corresponding to the dimers which dissociate into C$^{+}(^{2}$P)-He($^{1}$S) and C$^{+}(^{4}$P)-He($^{1}$S). This task is accomplished with \textsc{\textbf{molpro}}. Then, following the suggestions stated in a recent paper [1], we compute the energy-dependent thermophysical cross sections by using a full quantum-mechanical method, which yields in particular the quantal phase shifts. The final step aims at the use of the computed cross sections within the Viehland GRAMCHAR \textsc{\textbf{fortran}} code [2, 3] to get the mobility of the ions at fixed temperatures. The preliminary results are shown in the figure below.\\[4pt] [1] S. Matouba, H. Tanuma, and K. Ohtsuki, J. Phys. B \textbf{41,} 145205 (2008).\\[0pt] [2] L. Viehland, Chem. Phys. \textbf{179,} 71 (1994).\\[0pt] [3] L. Viehland, private communications. [Preview Abstract] |
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Q1.00140: An ultrafast molecular memory for light Philip J. Bustard, Rune Lausten, Duncan G. England, Benjamin J. Sussman Photonic devices of the future will require quantum memories capable of temporarily capturing, storing, and releasing photons while preserving the fidelity of quantum information.\footnote{A.~Lvovsky \emph{et al.} Nature Photon., \textbf{3}, 706 (2009)} For example, memories will enable synchronization of distinct photon channels, and compress processing times for algorithms using probabilistic photon sources. Here we discuss a room-temperature memory based on storing photons in the vibrations of molecules.\footnote{This work is under review for publication.} The memory utilizes the large energy level spacings afforded by molecules to allow high-bandwidth operation at room temperature, with no prior preparation of the initial molecular state. Photons are written into the molecular vibrations via a Stokes Raman transition, stored for a period, and read out using an anti-Stokes Raman transition. The ultra-broadband molecular memory has the potential to store femtosecond pulses for times approaching a nanosecond, permitting a large number of operational time bins, and making it a powerful tool for ultrafast local quantum processing, sufficient to build bench-top quantum architectures. [Preview Abstract] |
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Q1.00141: Absolute Photoionization of Rb$^{+}$ and Br$^{2+}$ Ions for the Determination of Elemental Abundances in Astrophysical Nebulae Allison Mueller, David Macaluso, Nicholas Sterling, Antonio Juarez, Ileana Dumitriu, Rene Bilodeau, Eddie Red, David Hardy, Alex Aguilar It has only recently become possible to detect neutron($n)$-capture elements in large numbers of ionized astrophysical objects. Measuring the abundances of these elements can reveal their dominant production sites in the Universe, as well as details of stellar structure, mixing, and nucleosynthesis. However, abundance determinations are highly dependent on the accuracy of the available atomic data. This has motivated an extensive laboratory astrophysics program to measure absolute single photoionization cross sections of the observed $n-$capture ion species. As part of this program, Rb$^{+}$ and Br$^{2+}$ ions have been measured at the Advanced Light Source at Lawrence Berkeley National Laboratory using the merged-beams technique. Both ions were measured from the metastable region to beyond their direct ionization threshold in a region rich with auto-ionizing resonances. Included in the analysis is the identification of several Rydberg series using quantum defect theory. This research was supported by the DOE, NASA, NASA/EPSCoR, and the Montana Space Grant Consortium. [Preview Abstract] |
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Q1.00142: Ramsey Interferometry of a Spin-1 Bose-Einstein Condensate Alexander Wood, Russell Anderson, Lincoln Turner Ramsey interferometry using ultracold atoms is a powerful technique in precision measurement. We report on using radiofrequency pulses to perform three-state Ramsey interferometry in a spin-1 Bose-Einstein condensate of $^{87}$Rb. The ground state phase diagram and dynamics of a spinor condensate are determined by two parameters: the density dependent spin-exchange interaction and the quadratic Zeeman shift. Ramsey interferometry probes the phase evolution of the condensate, and is sensitive to the small energy shifts ($\sim10\,\mathrm{Hz}$) resulting from these phenomena. The fidelity of the interferometer is dramatically improved by spin-echo pulses in the presence of parasitic noise and gradients of the background magnetic field. We demonstrate the high sensitivity of this method by measuring the influence of a microwave dressing field on the quadratic Zeeman shift, which we compare against a simple analytic model of the dressed system that accounts for the spin-exchange interaction. By varying the density of the condensate, the spin-exchange interaction may be measured precisely with our technique. We anticipate our results finding application in spinor collisional control studies and spatially resolved spin tomography of a spinor condensate. [Preview Abstract] |
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Q1.00143: Experimental distillation of quantum nonlocality Chong Zu |
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