Bulletin of the American Physical Society
46th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 60, Number 7
Monday–Friday, June 8–12, 2015; Columbus, Ohio
Session U3: Cold Molecules and Molecular Ions |
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Chair: Eric Hudson, University of California, Los Angeles Room: Franklin AB |
Friday, June 12, 2015 10:30AM - 10:42AM |
U3.00001: A cryogenic beam apparatus for laser cooling and ultracold fragmentation of BaH molecules Geoffrey Iwata, Marco G. Tarallo, Fabian Soerensen, Tanya Zelevinsky Cold and ultracold molecules offer a wide array of possibilities for precision measurement, molecular quantum chemistry, and studies many-body physics. Recently, cold beams of many molecular species have been created via cryogenic buffer gas cooling. Paired with laser cooling, this method can yield a molecular magneto-optical trap (MOT). We report progress toward a barium monohydride (BaH) cold molecular beam and MOT, including identification of cooling transitions in the $B^2\Sigma \leftarrow X^2\Sigma$ manifold in laser ablated molecules and construction of the cryogenic beam apparatus. The large mass ratio of the constituent atoms makes this system attractive for studies of ultracold fragmentation via coherent transfer to weakly bound states and subsequent photo- or magneto-dissociation, resulting in ultracold hydrogen. [Preview Abstract] |
Friday, June 12, 2015 10:42AM - 10:54AM |
U3.00002: Enhanced optical cycling and slowing of YO through rotational state microwave mixing Bo Yan, Matthew Hummon, Mark Yeo, Alejandra Collopy, Boerge Hemmerling, Eunmi Chae, Loic Anderegg, Aakash Ravi, John Doyle, Jun Ye In order to address rotational dark states in the molecule yttrium (II) monoxide (YO) and to enhance optical cycling, we demonstrate the remixing of ground electronic state rotational levels using microwave radiation. This mixing technique, in conjunction with a broadband modulated and frequency chirped laser, is used to decelerate a beam of YO from a cryogenic buffer gas cell. The result is a population of molecules with velocities less than 10 m/s, which are sufficiently slow to be loaded into a magneto-optical trap. With two vibrational repump lasers, the cycling transition is closed to the 10$^{-6}$ level. Additionally, we present progress towards a three dimensional implementation of a magneto-optical trap for YO. [Preview Abstract] |
Friday, June 12, 2015 10:54AM - 11:06AM |
U3.00003: Improved magneto-optical trapping of a diatomic molecule Eric Norrgard, Daniel McCarron, Matthew Steinecker, David DeMille The magneto-optical trap (MOT) is the workhorse technique for atomic physics in the ultracold regime, serving as the starting point in applications from optical clocks to quantum-degenerate gases. Recently, our group demonstrated the first magneto-optical trap for a molecule, strontium monofluoride (SrF). Here, we present experimental results of two variant trapping schemes which improve upon the original work. In the first [1], recent insights into the origin of the restoring force in Type-II MOTs [2] (rarely used for atoms but requisite for SrF and other candidate molecules) led to a simple change in polarization scheme for the MOT lasers. In the second, states dark to the restoring MOT beams are diabatically transferred to bright states by synchronously reversing the magnetic field gradient and the laser polarization at RF frequencies. Although magneto-optical trapping of diatomic molecules is in its infancy, our results indicate that access to the ultracold regime may be possible for several molecular species, with potential applications from quantum simulation to tests of fundamental symmetries to ultracold chemistry. \\[4pt] [1] McCarron D J, Norrgard E N, Steinecker M H and DeMille D, N J Phys 2015 (ArXiv prepint 1412.8220)\\[0pt] [2] Tarbutt M R, N J Phys 2015 (ArXiv prepint 1409.0244) [Preview Abstract] |
Friday, June 12, 2015 11:06AM - 11:18AM |
U3.00004: Formation of molecular ions by radiative association of cold trapped atoms and ions Olivier Dulieu, Humberto da Silva Jr, Mireille Aymar, Maurice Raoult Radiative emission during cold collisions between trapped laser-cooled Rb atoms and alkaline-earth ions (Ca+, Sr+, Ba+) and Yb+ are studied theoretically, using accurate effective-core-potential based quantum chemistry calculations of potential energy curves and transition dipole moments of the related molecular ions. Radiative association of molecular ions is predicted to occur for all systems with a cross section two to ten times larger than the radiative charge transfer one. Partial and total rate constants are also calculated and compared to available experiments. Narrow shape resonances are expected, which could be detectable at low temperature with an experimental resolution at the limit of the present standards. Vibrational distributions show that the final molecular ions are not created in their ground state level. [Preview Abstract] |
Friday, June 12, 2015 11:18AM - 11:30AM |
U3.00005: Progress on optical loading and laser cooling of the polyatomic molecule SrOH Louis Baum, Ivan Kozyryev, Kyle Matsuda, Boerge Hemmerling, John M. Doyle Polyatomic molecules hold promise for discovery of new physics and chemistry due to their rotational and vibrational degrees of freedom. We are approaching the production of ultracold SrOH by using buffer-gas cooling and optical manipulation. We report on the production of a cold and slow cryogenic buffer-gas beam [1] of SrOH containing 10$^9$ molecules per pulse of length a few ms with a peak forward velocity of 60 m/s and a velocity spread of 40 m/s. Using this beam, we have successfully demonstrated multiple-photon scattering on the X$^2\Sigma^{+}$-A$^2\Pi_{1/2}$ transition, which is a crucial step towards implementing laser cooling of a polyatomic. As a first application, we plan to use transverse laser cooling to decrease the intrinsic divergence of the beam source. We report on the progress towards optical loading such an enhanced, collimated beam of SrOH into a magnetic trap for studying atom-molecule collisions and exploring the possibility of sympathetic cooling for polyatomics with alkali atoms.\\[4pt] [1] Hutzler, Nicholas R., Hsin-I. Lu, and John M. Doyle. ``The buffer gas beam: An intense, cold, and slow source for atoms and molecules.'' Chemical Reviews 112.9 (2012): 4803-4827. [Preview Abstract] |
Friday, June 12, 2015 11:30AM - 11:42AM |
U3.00006: Rotational cooling of trapped polyatomic molecules Alexander Prehn, Rosa Gl\"{o}ckner, Martin Ibr\"{u}gger, Martin Zeppenfeld, Gerhard Rempe Potential applications of cold and ultracold polar molecules range from quantum simulations and quantum computing to precision measurements and cold chemistry. They would all benefit from the molecules' many states and long-range dipole-dipole interaction. A prerequisite for those applications is to gain and maintain control over all degrees of freedom. Here we present rotational-state cooling of methyl fluoride (CH$_3$F) via optical pumping. Starting from a thermal ensemble which is electrically trapped,\footnote{B.G.U. Englert {\it et al.}, Phys. Rev. Lett. {\bf 107}, 263003 (2011)} we optically pump the population from 16 rotational M-sublevels in four rotational states into a single level. Combining rotational-state control with motional Sisyphus cooling,\footnote{M. Zeppenfeld {\it et al.}, Nature {\bf 491}, 570-573 (2012)} we are able to produce a cold (30 mK) and nearly pure ensemble of CH$_3$F molecules with more than 70\,\% of all molecules populating a single rotational $M$-sublevel. Our scheme is easily extendable to larger sets of initial states and other molecule species thus paving the way to quantum-controlled experiments with polyatomic molecules. [Preview Abstract] |
Friday, June 12, 2015 11:42AM - 11:54AM |
U3.00007: Aspects of Quantum Computing with Polar Paramagnetic Molecules Mallikarjun Karra, Bretislav Friedrich Since the original proposal by DeMille, arrays of optically trapped ultracold polar molecules have been considered among the most promising prototype platforms for the implementation of a quantum computer. The qubit of a molecular array is realized by a single dipolar molecule entangled via its dipole-dipole interaction with the rest of the array's molecules. A superimposed inhomogeneous electric field precludes the quenching of the body-fixed dipole moments by rotation and a time dependent external field controls the qubits to perform gate operations. Much like our previous work in which we considered the simplest cases of a polar $^1\Sigma$ and a symmetric top molecule, here we consider a $X^2\Pi_{3/2}$ polar molecule (exemplified by the OH radical) which, by virtue of its nonzero electronic spin and orbital angular momenta, is, in addition, paramagnetic. We demonstrate entanglement tuning by evaluating the concurrence (and the requisite frequencies needed for gate operations) between two such molecules in the presence of varying electric and magnetic fields. Finally, we discuss the conditions required for achieving qubit addressability (transition frequency difference, $\Delta \omega$, as compared with the concomitant Stark and Zeeman broadening) and high fidelity. [Preview Abstract] |
Friday, June 12, 2015 11:54AM - 12:06PM |
U3.00008: Progress on Rotational Cooling of SiO+ Yen-Wei Lin, Patrick Stollenwerk, Brian Odom Producing ultracold molecules is the first step in precision molecular spectroscopy. Here we present some of the challenges and advantages of SiO+ as well as some of our progress toward meeting those challenges. To demonstrate ground state SiO+, we first load about 100 SiO+ via 2+1 REMPI into an ion trap. Translational motion of SiO+ is then sympathetically cooled by co-trapped Ba+, which is laser cooled. To prepare the population into the ground state, we optically pump the P-branch (rotational cooling transitions) in the B:$\Sigma$(v'=0) $\leftarrow$ X:$\Sigma$(v=0) band with broadband radiation. Because the band is highly diagonal, population can be effectively driven into the rotational ground state before falling into other manifolds. The broadband source, a fs laser, is spectrally filtered using an ultrashort pulse shaping technique to drive only the P-branch. Attention must be paid when aligning the optics to obtain sufficient masking resolution. We have achieved 3 cm$^{-1}$ resolution, which is sufficient to modify a broadband source for rotationally cooling SiO+. [Preview Abstract] |
Friday, June 12, 2015 12:06PM - 12:18PM |
U3.00009: Toward Quantum Logic Spectroscopy of Molecular Ions Christopher Seck, Matthew Dietrich, Mark Kokish, Brian Odom Quantum logic spectroscopy (QLS) demands reliable state preparation of the subject's external and internal quantum numbers, a challenging task for molecules owing to their numerous internal degrees of freedom. Having recently achieved rapid rotational ground state cooling with the aluminum monohydride cation (AlH$^{+}$)\footnote{C.-Y. Lien, C.S. Seck, Y.-W. Lin, J.H.V. Nguyen, D.A. Tabor, and B.C. Odom. Nat. Commun. \textbf{5}, 4783 (2014).}, we now present progress toward demonstrating QLS with AlH$^{+}$. We have implemented a new, efficient source for AlH$^{+}$ production via resonance enhanced multiphoton ionization (REMPI) of neutral aluminum monohydride (AlH). AlH is formed by ablation of aluminum in the presence of hydrogen gas. Following production, we then prepare the AlH$^{+}$ ions in a well-defined internal state. In addition, we demonstrate progress toward ground state cooling AlH$^{+}$ through sympathetic cooling with atomic barium ions (Ba$^{+}$). Ba$^{+}$ will then serve as our readout qubit in QLS. [Preview Abstract] |
Friday, June 12, 2015 12:18PM - 12:30PM |
U3.00010: Observation of Cs Trilobite and Butterfly Molecules Jin Yang, Donald Booth, Margarita Reschke, Seth Rittenhouse, Hossein Sadeghpour, James Shaffer Ultralong range Rydberg molecules formed by one Rydberg atom and one ground state atom through the low-energy scattering of a Rydberg electron from the nearby ground state atom are attracting more and more interest because of the novel physics associated with them, such as the generation of kilo-Debye dipole moments. We report on our work on these molecules including the observation of ultralong range trilobite and butterfly molecules for Cs s-states. We compare and contrast these results to what has been observed in Rb experiments and new work of ours on Cs d-states. The experiments and theory directly show the role of state mixing, p-wave scattering resonances, and the Rydberg state structure of the Rydberg atoms involved in the formation of ultralong range Rydberg molecules. [Preview Abstract] |
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