Bulletin of the American Physical Society
40th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 54, Number 7
Tuesday–Saturday, May 19–23, 2009; Charlottesville, Virginia
Session Y1: Poster Session IV (1:30 - 3:30 pm) |
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Room: Newcomb Hall Ballroom |
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Y1.00001: ATOMIC AND MOLECULAR STRUCTURE AND PROPERTIES |
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Y1.00002: Atomic Spectra Bibliography Databases at NIST Alexander Kramida NIST's Atomic Spectroscopy Data Center maintains three online Bibliographic Databases (BD) containing references to papers with atomic data for controlled fusion research, modeling and diagnostics of astrophysical and terrestrial plasmas, and fundamental properties of electronic spectra of atoms and ions. The NIST Atomic Energy Levels and Spectra BD [http://physics.nist.gov/elevbib] now includes about 14500 references, mostly for years 1967--2009. The NIST Atomic Transition Probability BD, v.~8.1 [http://physics.nist.gov/fvalbib] with its 8000 references mainly covers years 1964--2008. The NIST Spectral Line Broadening BD, v.~2.0 [http://physics.nist.gov/linebrbib] has 4000 references, mostly for 1975--2008. All three databases are regularly updated with current publications. During the last year, the literature on atomic spectroscopy was reviewed for publication years 1990 through 2005, which significantly improved the coverage in all three BDs. We continue the work to include papers published before 1975 in the Line Broadening BD. [Preview Abstract] |
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Y1.00003: Binding energy calculations for e$^{+}$Li and e$^{+}$Na Janine Shertzer, S.J. Ward In order to calculate the binding energy of e$^{+}$Li and e$^{+}$Na, we treat the positronic ions as effective three-body systems. The interaction between the electron/positron and the ionic core is described by the Peach model potential. This $l-$independent parametric model potential yields energy levels which are in excellent agreement with measurements of the alkali spectra. Although the model potential gives rise to a spurious 1s state for Li (and spurious 1s, 2s, 2p states for Na), these states are easily identified. The wave function associated with the true physical ground state has the correct nodal structure in the radial coordinate. For the effective three-body system, there is a series of spurious states which are also easily identified by the nodal structure and the value of $\langle r_{-}\rangle $. In practice, we never calculate these states, but search for solutions using a Rayleigh quotient iteration method with a starting eigenvalue slightly less than the ground-state energy of the alkali atom. Our results for e$^{+}$Li are in good agreement with previous calculations using the exact Hamiltonian and an adiabatic hyperspherical calculation. For e$^{+}$Na, this is the first non-adiabatic calculation for the binding energy. [Preview Abstract] |
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Y1.00004: Calculation of Atomic Parameters of multiply-stripped Atoms Khondkar Karim We present theoretical transition rates, transition energies, fluorescence and Auger yields, and satellite intensity factors, for several atoms with configurations $n_1l_1^{q_1}n_2l_2^{q_2}$ and $n_1l_1^{q_1}n_2l_2^{q_2}n_3l_3^{q_3}$ for various values of $q_1$, $q_2$, $q_3$, and $n_1$, $n_2$, and $n_3$. The Hartree-Fock and Hartree-Fock-Slater atomic models were used to generate the wave functions. The calculation was performed in intermediate coupling scheme with inclusion of configuration interaction effects. [Preview Abstract] |
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Y1.00005: Wavelengths and transition rates for $nl-n'l'$ transitions in Na-, Mg-, Al-, K-, Ca-, Zn-, Cd-, and Yb-like tungsten ions A.S. Safronova, U.I. Safronova Energies of levels with 1, 2, and 3 electrons above the closed shell in W ions are calculated. In particular, energies of Na- like ([Ne]$nl, n=3, 4$), Mg-like ([Ne]$3l3l'$), Al-like ([Ne]$3l3l'3l''$), K-like ([Ar]$nl, n=3, 4$), Ca-like ([Ar]$3d4l$), Zn-like ([Ni]$4l4l'$), Cd-like [Kr]$4d^{10}4f5l$), Yb-like ([Xe]$4f^{14}5l5l'$) tungsten are computed by relativistic many-body perturbation theory method (RMBPT code), the Multiconfiguration Relativistic Hebrew University Lawrence Atomic Code (HULLAC code), and the Hartree-Fock-Relativistic method (Cowan code). Wavelengths, transition rates, and line strengths are calculated for the dipole $nl-n'l'$ transitions in Na-, Mg-, Al-, K-, Ca-, Zn-, Cd-, and Yb-like tungsten ions. A detailed discussion of the various contributions to the dipole matrix elements and energy levels given by different codes is provided. These atomic data are important in modeling of M-, N-, and O- shell radiation spectra of heavy ions generated in various collision as well as plasma experiments. The tungsten data are particulary important for fusion application. [Preview Abstract] |
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Y1.00006: Computational efficiences for calculating rare earth $f^n$ energies Donald R. Beck Recently\footnote{D. R. Beck and E. J. Domeier, Can. J. Phys. Walter Johnson issue, Jan. 2009.}, we have used new computational strategies to obtain wavefunctions and energies for Gd IV $4f^7$ and $4f^65d$ levels. Here we extend one of these techniques to allow efficent inclusion of $4f^2$ pair correlation effects using radial pair energies obtained from much simpler calculations\footnote{e.g. K. Jankowski \textit{et al.}, Int. J. Quant. Chem. \textbf{XXVII}, 665 (1985).} and angular factors which can be simply computed\footnote{D. R. Beck and C. A. Nicolaides, Excited States in Quantum Chemistry, C. A. Nicolaides and D. R. Beck (editors), D. Reidel (1978), p. 105ff.}. This is a re-vitalization of an older idea\footnote{I. Oksuz and O. Sinanoglu, Phys. Rev. \textbf{181}, 54 (1969).}. We display relationships between angular factors involving the exchange of holes and electrons (e.g. $f^6$ vs $f^8$, $f^{13}d$ vs $fd^9$). We apply the results to Tb IV and Gd IV, whose spectra is largely unknown, but which may play a role in MRI medicine as endohedral metallofullerenes (e.g. Gd$_3$N-C$_{80}$\footnote{M. C. Qian and S. N. Khanna, J. Appl. Phys. \textbf{101}, 09E105 (2007).}). Pr III results are in good agreement (910 cm$^{-1}$) with experiment. Pu I $5f^2$ radial pair energies are also presented. [Preview Abstract] |
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Y1.00007: Valence calculations of lanthanide anion binding energies: a comprehensive study Steven M. O'Malley, Donald R. Beck We have applied a methodology of universal $jls$ restrictions on the $4f^n$ subgroup of relativistic configuration-interaction calculations of progressively more complex lanthanide anions\footnote{S. M. O'Malley and D. R. Beck, Phys. Rev. A \textbf{77}, 012505 (2008).}$^{,}$\footnote{S. M. O'Malley and D. R. Beck, Phys. Rev. A \textbf{78}, 012510 (2008).}$^{,}$\footnote{S. M. O'Malley and D. R. Beck, Phys. Rev. A, in press.}. Our completed study of the row predicts bound $6p$ attachments to all lanthanide ground state configurations except Yb, additional $6p$ attachments to excited opposite parity configurations in Tb and Lu, and $6s$ attachments to excited open-$6s$ thresholds in La, Ce, Pr, and Gd. In total we predict more than 100 bound states for the lanthanide anions, and we hope this comprehensive study encourages further experimental\footnote{e.g. V. T. Davis \textit{et al.}, Nucl. Instrum. Methods Phys. Res. B \textbf{241}, 118 (2005).}$^{,}$\footnote{e.g. C. W. Walter \textit{et al.}, Phys. Rev. A \textbf{76}, 052702 (2007).} interest in these anions. Such measurements will be useful in ``fine tuning'' these \textit{ab initio} binding energies to account for missing core-valence correlation and the approximations that were necessary in these complex calculations. [Preview Abstract] |
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Y1.00008: Hyperfine quenching of $(3d^94s)\, ^3$D$_3$ states in Ni-like ions Walter Johnson, Ulyana Safronova We study quenching of decays from metastable ($3d^9\,4s$) $^3$D$_3$ states of Ni-like ions with odd-A nuclei caused by hyperfine mixing with nearby $^{1,3}$D$_2$ states. A detailed discussion is given for the Ni-like ions $^{132}$Xe, $^{131}$Xe, and $^{129}$Xe. For $^{132}$Xe ($I$=0) the $^3$D$_3$ state decays by M3 emission. For the odd-A nuclei $^{131}$Xe ($I$=3/2) and $^{129}$Xe ($I$=1/2), each hyperfine level decays at a separate rate owing to hyperfine mixing. Comparisons are made with other calculations [1] and with experiment [2] for the the three isotopes of Ni-like Xe. Decay rates of the hyperfine levels of $^3$D$_3$ states are evaluated for isotopes of those Ni-like ions in the range $^{77}$Se$^{8+}$ -- $^{207} $Pb$^{54+}$ that have nuclear spin $I$=1/2 using relativistic many-body perturbation theory.\vspace{0.25pc} \noindent [1]\ K. Yao, M. Andersson, T. Brage, R. Hutton, P. J\"{o}nsson, and Y. Zou, Phys.\ Rev.\ Lett.\ {\bf 98}, 269903 (2007). \noindent[2]\ E. Tr\"{a}bert, P. Beiersdorfer, and G. V. Brown, Phys.\ Rev.\ Lett.\ {\bf 98}, 263001 (2007). [Preview Abstract] |
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Y1.00009: Autler-Townes splitting in a spin-orbit mixed singlet-triplet pair of rovibrational levels of the Lithium dimer molecule Jianbing Qi, Marjatta Lyyra We demonstrate Autler-Townes splitting in a singlet-triplet pair of ro-vibrational levels perturbed by the spin orbit interaction in the Lithium dimer molecule using cw lasers. The two upper excited spin-orbit mixed singlet-triplet molecular rovibrational levels are coupled by a stronger cw coupling laser to an auxiliary lower rovibrational level, which results in Autler-Townes splitting or ac Stark shift of the coupled levels. The splitting depends on the strength and the detuning of the coupling laser. The excitation spectra and the splitting lineshape were obtained by detecting the fluorescence from the mixed pair following optical-optical double resonance excitation. The preliminary density matrix equation analysis of the experimental spectra is in good agreement with the experimental data. Supported by NSF PHY 0555608, the Lagerqvist Fund of Temple University, and Penn State Research and Development Grant. [Preview Abstract] |
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Y1.00010: FUNDAMENTAL SYMMETRIES AND PRECISION MEASUREMENTS |
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Y1.00011: Lorentz Symmetries of a Doubly Hyperbolic Phase Space Felix T. Smith The Einstein addition law of velocities implies a hyperbolic geometry for relativistic velocity and momentum space. The simplest model of an open, expanding universe implies a hyperbolic geometry for position space. It is natural to investigate the kinematics of a phase space combining hyperbolic geometries in both the velocity-momentum manifold H(3)$_{\mbox{vel}}$ and the position manifold H(3)$_{\mbox{pos}}$. Each of these sustains its own Lorentz subgroup, L$_{\mbox{vel}}$ = O(1,3)$_{\mbox{vel}}$ and L$_{\mbox{pos}}$ = O(1,3)$_{\mbox{pos}}$. These form a direct product group L$^2$ = L$_{\mbox{vel}} \times$ L$_{\mbox{pos}}$, a 12-parameter group, represented by 8 $\times 8$ matrices. Among its operators are a subgroup L$_{\mbox{boost}}$ of Lorentz velocity boosts that operate on the elements of L$_{\mbox{vel}}$ by Einstein addition and on those of L$_{\mbox{pos}}$ by the Lorentz transformation. There is also a conjugate subgroup L$_{\mbox{shift}}$ of hyperbolic translational shifts that operate on the elements of L$_{\mbox{pos}}$ translationally, and on those of L$_{\mbox{vel}}$ to describe the Hubble effect of distance on velocity vectors. The structure, symmetries, Lie algebra and important operators and quantum numbers of the resulting representation of L$^2$ will be reported. (See also F.T. Smith, Ann. Fond. L. de Broglie, 30, 179 (2005).) [Preview Abstract] |
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Y1.00012: Rotational Consequences of Lorentz Symmetries in Hyperbolic Phase Space Felix T. Smith A hyperbolically curved position space when combined with a relativistic velocity-momentum space forms a phase space with the symmetries of a direct product double Lorentz group, expressed by $8\times 8$ matrices. (See an adjoining Abstract, ``Lorentz Symmetries of a Doubly Hyperbolic Phase Space.'') Its rotational subgroup too is a direct product, combining rotations in position space with those in momentum space to form a total angular momentum $\bf J$ and an unfamiliar contra-angular momentum $\bf Q$, a pseudovector whose coupling with other vectors vanishes in the absence of spatial and velocity space curvature. Its quantum numbers and properties may label some particle states. The second-order couplings populating states of $\bf Q$ arise from a combination of both position and velocity space curvatures; they are comparable in nature to the Thomas precession process, which can itself be looked upon as a second-order effect of curvature in relativistic velocity space. Processes altering $\bf Q$ values will therefore occur preferentially at relativistic velocities in regions of high gravitational curvature. [Preview Abstract] |
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Y1.00013: Micromagic clock: microwave clock based on atoms in an engineered optical lattice Andrei Derevianko, Kyle Beloy, Vladimir Dzuba, Victor Flambaum We propose a new class of atomic microwave clocks based on the hyperfine transitions in the ground state of aluminum or gallium atoms trapped in optical lattices. For these elements {\em magic} wavelengths exist at which both levels of the hyperfine doublet are shifted at the same rate by the lattice laser field, cancelling its effect on the clock transition. This work represents an elegant piece of theoretical physics containing a challenge to the experimentalist to realize a new frequency standard based on these proposed clocks. [Preview Abstract] |
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Y1.00014: Precision Measurements with an 87Sr Optical Lattice Clock Travis Nicholson, Gretchen Campbell, Sebastian Blatt, Michael Martin, Matt Swallows, Andrew Ludlow, Martin Boyd, Jan Thomsen, Jun Ye The uncertainty of our $^{87}$Sr optical lattice clock operating on the ultranarrow $^1S_0$-$^3P_0$ transition has recently reached 1.5$\times 10^{-16}$. We will report our latest work in further reducing this uncertainty. One of the largest frequency shifts---a density shift---has now been characterized at the $5 \times 10^{-17}$ level. An understanding of the measurement-induced Fermionic interactions at ultracold temperatures has allowed us to zero the density shift altogether by operating the clock near a 50\% excitation fraction. Furthermore, we report advancements in characterizing blackbody radiation-induced clock shifts. Recent progress toward high-fidelity manipulations of the long-lived nuclear- and electronic-spin states in alkaline earth atoms, a capability that will be useful for neutral-atom-based quantum information processing, will also be presented. [Preview Abstract] |
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Y1.00015: Matter-Wave Interferometery at BYU Christopher Erickson, James Archibald, Daniel Merrill, Aaron Bennett, Dallin Durfee We report on the progress of two matter-wave interferometers at BYU. The first device is a thermal-beam Ramsey-Bord\a'e calcium interferometer. The second device is an ion interferometer based on a laser-cooled $^{87}$Sr$^+$ beam which will be split and recombined using stimulated Raman transitions. Design considerations, instrumentation development, and possible applications of the devices will be discussed. [Preview Abstract] |
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Y1.00016: A 150 ppb Microwave Measurement of the n=2 Triplet P J=1-to-J=2 Fine-Structure Interval of Helium J.S. Borbely, M.C. George, L.D. Lombardi, M. Weel, D.W. Fitzakerley, E.A. Hessels The n=2 triplet P J=1-to-J=2 interval in helium has been measured to a precision of 350 Hz using the Ramsey method of separated oscillatory field. This 350 Hz measurement is the most precise to date of the n=2 triplet structure. Comparison between precise measurements of the n=2 triplet P fine structure and theoretical predictions will allow for a precise determination of the fine-structure constant when the current large discrepancy between experiment (PRL \underline {95} 203001; PRL \underline {87} 173002; PRL \underline {84} 4321; Can J Phys \underline {83} 301) and theory (PRL \underline {97} 013002; Can J Phys \underline {80} 1195) is resolved. [Preview Abstract] |
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Y1.00017: Environment assisted diamond magnetometry: Environment-assisted precision measurements using solid-state spin Garry Goldstein, Paola Cappelaro, Jero Maze, Liang Jiang, Misha Lukin Isolated electronic spins in the solid-state, such as the Nitrogen-Vacancy (NV) center in diamond, have been recently proposed as sensitive magnetic sensors. We propose a method for enhancing magnetic field sensitivity by using the ``dark'' spins in NV center environment to amplify the system response to external magnetic fields. We describe a strategy to partially polarize and control the environment spins for maximal response. The signal enhancement is proportional to the number of environment spins coupling ``strongly'' to the central spin and to their degree of polarization. The method success does not rely on the exact value of the couplings between the bright spin and the environment spins, but on the existence of many nitrogen spins that couple to the central spin more strongly than relevant decoherence rates. For high density of the environment spins the proposed method could improve the sensitivity by a factor of T2 /T2 * . [Preview Abstract] |
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Y1.00018: Improved measurements of the cesium $nd$ hyperfine structure using photoion spectroscopy of a thermal beam Andrew Kortyna, Jennifer Grab The $6d \, ^2 \! D_{3/2}$ and $7d \, ^2 \! D_{3/2}$ states of $^{133}$Cs are studied using photoion spectroscopy. The goal is to improve measurements of the associated hyperfine coupling constants. Two single-mode, external-cavity diode lasers counter-propagate normal to a collimated thermal beam of cesium. The first laser is center locked to the $6s \, ^2 \! S_{1/2} \rightarrow 6p \, ^2 \! P_{1/2}$ transition, and the second laser is scanned across the $6p \, ^2 \! P_{1/2} \rightarrow nd \, ^2 \! D_{3/2}$ manifold. Photoions are produced by absorption of a third photon, and ions are analyzed in a time-of-flight mass spectrometer. The frequency scale of the second laser is calibrated through phase modulation at a precise frequency. Photoion spectroscopy has high collection efficiency and low background, producing improved sensitivity compared to the more common technique of fluorescence spectroscopy. This improved sensitivity allows for lower laser power, minimizing power-broadening. Fast scans are also permitted, reducing the effect of thermal drifts on the frequency resolution. [Preview Abstract] |
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Y1.00019: PHOTON INTERACTIONS WITH ATOMS, IONS, AND MOLECULES |
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Y1.00020: Application of the Velocity Map Imaging Technique for Low Kinetic Energy Photoelectrons Eddie C. Red, Antonio M. Ju\'arez, Matthias Hoener, Daniel Rolles, Alejandro Aguilar A modified Velocity Map Imaging (VMI) spectrometer has been used with synchrotron radiation at the Advanced Light Source at Lawrence Berkeley National Laboratory to study the photoelectron angular distributions (PADs) of near-zero kinetic energy (5 meV -- 100 meV) photoelectrons. Beta asymmetry parameter measurements are a useful tool for gaining insight into the dynamics associated with electron correlation effects. ``Proof of Principle'' experiments were conducted near the ionization thresholds of helium and neon to test the suitability of the VMI apparatus for the measurement of PADs. Electron-ion coincidence experiments are underway to study the double photoionization of helium at energies less than 100 meV above the ionization threshold. [Preview Abstract] |
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Y1.00021: Electromagnetically induced transparency in a multi-level system of Doppler-broadened Cesium atom Chin-Chun Tsai, Ming-Tsung Lee, Ray-Yuan Chang Doubly dressed electromagnetically induced transparency in a multi-level ladder-type system of Doppler-broadened cesium atom is observed. These doubly-dressed states are established by using a strong coupling laser and a moderate probe laser in a multi- level atomic configuration. The probe laser was locked at the hyperfine transition $|6S_{1/2},F^{\prime\prime}=4\rangle\leftrightarrow |6P_{3/2},F^\prime=4\rangle$ of Cs atom while the coupling laser scanned from $|6P_{3/2},F^\prime\rangle$ levels across the $|8S_ {1/2},F=3\rangle$ and $|8S_{1/2},F=4\rangle$ levels. These two laser beams were counter-propagated and overlapped inside the Doppler-broadened cesium cell under room temperature. Hyperfine levels of $|6P_{3/2},F^\prime\rangle$ serve as a doubly-dressed intermediated states for this ladder-type transitions. The absorption spectra of different probe laser intensity are investigated. Numerical simulation based on solving the steady-state Bloch equations can fit the observed spectrum well. [Preview Abstract] |
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Y1.00022: Diffraction light measurements of emission europium in a waveguide of planar metallic walls. Aldo S. Ramirez Duverger, Raul Aceves, Raul Garcia-Llamas, Jorge Gaspar-Armenta, Vladimir Ramirez Experimental results of diffraction light measurements of europium ions emission in a MgF$_{2}$ waveguide between Al metallic walls are reported. In this structure the reflected light is confined to travel along the guide. From the spectral reflection curves were determinates the conditions of better coupling mode - incident light. The luminescence of Eu$^{2+}$ in polycrystalline MgF$_{2}$ and in the waveguide was found to have a maximum at 440 nm. This emission was ascribed with electronic transitions of Eu$^{2+}$ ions dipoles on a lattice of MgF$_{2}$. For an excitation light of 360 nm, the integrated emission versus incident angle was measured to find the incident angle were the emission reach their maximum value. This behavior is explained because for that excitation light and incident angle a guided mode along the waveguide is produced and more emitters are excited in the optical path of the reflected light. [Preview Abstract] |
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Y1.00023: Time-resolved core-hole decay and sideband structure in laser-assisted photoemission from metal surfaces Chang-hua Zhang, Uwe Thumm We present a theoretical investigation of sideband structures in laser-assisted photoelectron spectra that result from the illumination of an adsorbate-covered metal surface with an ultra-short soft X-ray and a delayed IR laser pulse. We show how the relaxation dynamics of core level holes in the adsorbate atoms can be deduced from a temporal shift in the intensity of the first sideband peaks of adsorbate-Auger electrons relative to conduction band photoelectrons. Our results also include a characteristic sub-sideband structure in the photoelectron spectra that is due to the interference of core-level electrons which are emitted from different layers in the solid. [Preview Abstract] |
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Y1.00024: X-Ray Photoabsorption in Magnesium Ions Sh. A. Abdel-Naby, M.F. Hasoglu, D. Nicoli\'c, T.W. Gorczyca K-shell photoabsorption cross sections are necessary for determining elemental abundances of the interstellar medium (ISM) from observed X-ray spectra. Over the past few years, our group has computed reliable K-shell photoabsorption calculations for oxygen [1-3], neon [4,5], and carbon [6] ions. We extend our calculations to magnesium ions using a state-of-the-art R-matrix method that incorporates the important Auger broadening and pseudoresonanace-elimination effects. Comparisons with available independent-particle (IP) results and other available data will also be presented. \newline \newline This work was supported in part by NASA's Astronomy Physics Research and Analysis (APRA) and Solar and Heliospheric Physics (SHP) Supporting Research and Technology (SR\&T) programs. \newline \newline [1] T. W. Gorczyca and B. M. McLaughlin. J Phys. B. {\bf 33}, L859 (2000). \newline [2] A. M. Juett, {\it et al}., Astrophys. J. {\bf 612}, 308 (2004). \newline [3] J. Garcia {\it et al}, Astrophys. J. Supp. S. {\bf 158}, 68 (2005). \newline [4] T. W. Gorczyca., Phys. Rev. A. {\bf 61}, 024702 (2000). \newline [5] A. M. Juett, {\it et al}, Astrophys. J. {\bf 648}, 1066 (2006). \newline [6] M. F. Hasoglu, {\it et al}, Astrophys. J., (in preparation) [Preview Abstract] |
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Y1.00025: Interactions of cold atoms and ultrafast laser pulses Michelle Stephens, Kyle Taylor, Jacob Berg, Joseph Hottenstein, Hai Nguyen, Christopher Verzani We report experimental progress of the interaction between cold trapped atoms and ultrafast laser pulses. At the University of Wisconsin Stevens Point, we use a Spectra-Physics Millennia laser to pump a KM Labs Ti:Sappire laser which produces pulses with duration of about 30 fs at a wavelength of 800 nm at a repetition rate of 1 kHz. Investigations of the interactions of these ultrafast laser pulses with 300 micro K Rb atoms produced in a magneto optical trap are underway. We look for various processes of molecular photo-association which include formation, distribution of populations, and alignment. The diagnostic system and the specific photo-association process will be described in detail. [Preview Abstract] |
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Y1.00026: Tunable left-right asymmetry in the dissociation of D$_2^+$ in a two-color laser field Feng He, Dipanwita Ray, Sankar De, Igor Litvinyuk, Lew Cocke, Uwe Thumm The coherent superposition of a linearly polarized intense IR laser pulse with its first harmonic generates a two-color pulse whose asymmetric shape is controlled by the adjustable delay $\tau$ between the two pulses. By numerically solving the time-dependent Schr\"odinger equation, we simulate the dissociation of D$_2^+$ in such pulses and analyze the left-right asymmetry in the electron-localization during the dissociation of the molecular ion as a function of $\tau$ and the kinetic energy of the fragments. Our theoretical results are compared with new experimental results from the J.R. Macdonald Laboratory at KSU. [Preview Abstract] |
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Y1.00027: THE ULTRA INTENSE LASER FRONTIER PROCESSES |
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Y1.00028: Using the harmonic Faraday instability to create fluid targets having application in laser-driven fusion Tom Donnelly, Nate Jones, Aaron Guillen, Andrew Bernoff, Andrew Higginbotham We predict a transition from sub-harmonic to harmonic Faraday waves for a deep, inviscid fluid at sufficiently large excitation amplitudes and frequencies. The transition is observed experimentally in the ultrasonic (MHz) frequency range using piezoelectric oscillators submerged in a water bath to drive the waves. The submerged oscillator atomizes the fluid, creating droplets with submicron radii. The size of the droplets is measured using Mie scattering, and is consistent with the predicted transition from subharmonic to harmonic Faraday waves. These small droplets are used as targets in experiments which demonstrate laser-driven fusion. [Preview Abstract] |
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Y1.00029: Ultrafast electron dynamics in rare gas clusters under X-FEL light Jan Michael Rost, Christian Gnodtke, Ulf Saalmann Time resolved imaging with Angstrom resolution is one of the prime goals to use XFEL light for. Here we investigate in detail the dynamics of electrons and ions of a cluster exposed to a realistic X-FEL pulse. We focus on electron migration phenomena and investigate their role under the aspect of harm and benefit for imaging the cluster structure. Field ionization processes turn out to play an important role where the electric field is generated by quickly formed ions [1]. We also propose an experiment with double pulse of 1 fs duration each, separated by 10-100 fs which can be realized at LCLS in Stanford. With this pump-probe scenario, the dynamics of Auger processes in rare gas clusters (here Ne) can be studied which promises to be interesting since it differs from the isolated atom due to the neighboring ions/atoms [2]. \\[4pt] [1] Ch. Gnodtke, U. Saalmann, Jan M. Rost, submitted (2009).\\[0pt] [2] Ulf Saalmann and Jan M. Rost, Phys. Rev. Lett. 89, 143401 (2002). [Preview Abstract] |
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Y1.00030: SHORT PULSE PROCESSES |
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Y1.00031: Study of the possibility of extracting single-atom photo-recombination cross sections from macroscopic high harmonic spectra generated by lasers. Cheng Jin, Anh-Thu Le, Chii-Dong Lin We examined the possibility of extracting photo-recombination dipole moment of single atoms from high-order harmonics generation (HHG) after the harmonics have propagated through the macroscopic medium. We compare the HHG spectra of Ar by solving the propagation equations using single-atom harmonics calculated from the strong field approximation (SFA), the quantitative rescattering model (QRS) and the time-dependent Schr\"{o}dinger equation (TDSE). We further show that the macroscopic HHG spectra can be expressed as the product of a macroscopic wave packet with the single-atom recombination cross section, and the extracted wave packet for Ar, Xe and Ne, under the same laser condition are almost the same, and independent of whether SFA, QRS or TDSE are used for the single-atom calculations. This theoretical result confirms that one can extract photo-recombination cross section from macroscopic HHG spectra by comparing spectra from different targets. [Preview Abstract] |
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Y1.00032: Angular and Intensity Dependent Spectral Modulations in High Harmonics from N$_2$ Brian McFarland, Joseph Farrell, Philip Bucksbaum, Markus Guehr The spectral amplitude and phase modulation of high harmonics (HHG) in molecules provides important clues to molecular structure and dynamics in strong laser fields. We have studied these effects in aligned N$_2$. Earlier results of HHG experiments claimed that the spectral amplitude modulation was predominantly due to geometrical interference between the recombining electron and the highest occupied molecular orbital (HOMO) [1]. We report evidence that contradicts this simple view. We observe a phase jump accompanied by a spectral minimum for HHG in aligned N$_2$. The minimum shifts to lower harmonics as the angle between the molecular axis and harmonic generation polarization increases, and shifts to higher harmonics with increasing harmonic generation intensity. The features observed cannot be fully explained by a geometrical model. We discuss alternative explanations involving multi orbital effects [2]. \\[0pt] [1] Lein et al., Phys. Rev. A, 66, 023805 (2002) [2] B. K. McFarland, J. P. Farrell, P. H. Bucksbaum and M. G\"uhr, Science 322, 1232 (2008) [Preview Abstract] |
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Y1.00033: Resonance-Enhanced Multiphoton Processes by Means of High-Order Harmonic Generation Precision Comb Spectroscopy. Juan J. Carrera, Shih-I. Chu Resonance-enhanced multiphoton transitions take place when a train of time-delayed coherent pulses interact with atomic systems. We accurately probe the first five excited electronic states and their corresponding transitions to the ground state. As the density of the frequency comb modes increases around each resonance frequency with increasing time delay, simultaneous comb modes of the driving laser field greatly amplify the low-lying transitions to the ground state. The spectral comb modes are farther fine-tuned by adjusting the offset angular frequency controlled by the pulses-to-pulse laser phase difference. In addition, we investigate n-photon excitation processes indicating the existence of n-resonance peak positions of the offset angular frequency. [Preview Abstract] |
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Y1.00034: ELECTRON-ATOM COLLISIONS |
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Y1.00035: Low-Energy Electron Elastic Differential Cross Sections for Lanthanide Atoms A.Z. Msezane, Z. Felfli, D. Sokolovski Recently [1] the near-threshold electron attachment mechanism in electron-lanthanide atom scattering was investigated using the recently developed Regge-pole analysis through the calculation of the electron elastic total cross sections (TCSs) [2]. Generally, the TCSs were found to be characterized by extremely narrow resonances whose energy positions were identified with the binding energies (BEs) of the negative ions formed during the collisions as Regge resonances. Here we have selected typical lanthanides, determined through their formation of tenuously bound (BE $<$ 0.1eV), weakly bound (BE $<$ 1eV) and complicated open d- and f-sub-shell negative ions in the near-threshold electron elastic scattering, to investigate the structure of their differential cross sections (DCSs) in angle in the electron impact energy range 0$<$ E $\le $ 1eV. The DCSs in energy at scattering angles $\theta $ = 0\r{ }, 90\r{ } and 180\r{ } are presented as well; these readily yield the BEs of the negative ions formed during the collisions [3]. Consequently, a new simple experimental procedure is suggested for measuring reliably the BEs of negative ions in general. Also determined are the so-called DCS critical minima. [1] Z. Felfli \textit{et al}, Phys. Rev. A \textbf{79}, At Press (2009) [2] D. Sokolovski \textit{et al}, Phys. Rev. A\textbf{76}, 012705 (2007) [3] Z. Felfli \textit{et al,} Phys. Rev. A \textbf{78}, 030307 (R) (2008) Supported by U.S. DOE, Division of Chemical Sciences. [Preview Abstract] |
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Y1.00036: Electron Spectroscopy of Tenuously and Weakly Bound Negative Ions A.Z. Msezane, Z. Felfli, D. Sokolovski We propose using very slow electron elastic collisions with atoms to identify their presence through observation of tenuously bound (impact energy, E$<$0.1 eV) and weakly bound (E$<$0.2 eV) negative ions, formed during the collisions. This could be important in identifying the presence of atoms in various environments. In an appropriate representation the characteristic very sharp resonances in electron-atom elastic total cross sections (TCSs) are enhanced significantly. Their positions yield the binding energies of the negative ions formed as Regge resonances, identified through the careful scrutiny of the complex angular momentum L. Two limiting curves determine the behavior as E$\to $ 0. The TCSs for example Tm, Sr and Mn in the region of formation of their tenuously bound negative ions with Re L=2 electron attachment follow a Wigner threshold law determined by the lowest Regge trajectory. Resonances in TCSs for the group exemplified by Cd, Eu and Tc atoms forming weakly bound negative ions with Re L=3 electron attachment rest on a trajectory that approaches that for e-Ca scattering, with Re L=1 electron attachment. The calculations used the Regge-pole methodology with a Thomas-Fermi type potential [1, 2]. [1] D. Sokolovski \textit{et al}, Phys. Rev. A\textbf{76}, 012705 (2007). [2] Z. Felfli \textit{et al}, Phys. Rev. A\textbf{78}, 030703 (R) (2008). Supported by US DOE Office of Basic Energy Sciences. [Preview Abstract] |
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Y1.00037: Theoretical and Experimental Studies for Electron Impact Ionization for Argon and Xenon Measured in the Perpendicular Plane Ola Al-Hagan, Christian Kaiser, Andrew Murray, Don Madison Our recent study using the three body distorted wave (3DW) approximation method showed good agreement with experimental measurements for fully differential cross sections (FDCS) for the ionization of both H2 and He by electron impact in a plane perpendicular to the incident beam. New physical effects were found in the perpendicular plane which had not previously been seen in studies limited to the scattering plane. The large differences between He and H2(same number of electrons and protons) were attributed to the nuclear charge distributions. The purpose of this work is to extend the perpendicular plane studies to heavier targets and ionization of p-shells. Experimental and theoretical results will be presented ionization of argon and xenon for case in which both final state electrons have the same energy ranging between 1 eV to 25 eV. [Preview Abstract] |
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Y1.00038: Low Energy Electron Impact Ionization of Neon and Xenon Brent R. Yates, Kyle Keane, Murtadha A. Khakoo Experimental doubly differential cross-sections for electron impact ionization of Neon and Xenon will be presented. The measurements were taken at incident energies ranging from near-threshold to below the second ionization threshold of the target and are the only set of data present in this range. Despite the fact that the targets are left similarly with an ionized P-core, the results show significant differences between the targets in terms of angular distributions as well as the shapes of single differential cross-sections for these two targets, and imply dynamics in the post collision which differ between the two targets, and suggest that relativistic effects (spin-orbit coupling) may be important. [Preview Abstract] |
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Y1.00039: Electron impact ionization of atomic targets at relativistic energies M.A. Uddin, A.K. Basak, B.C. Saha The huge demand and scarcity of electron impact ionization cross sections (EIICS) that are essential not only in modeling but also in basic researches can be best filled in by simple to use analytical models [1] that are sufficiently accurate and provide fast generation of EIICS data over wide domain. We report few such models and compare their productive powers in terms of few adjustable parameters. Details of our results will be presented in the conference. [1] A. K. F. Haque, M. A. Uddin, A. K. Basak, K. R. Karim, B. C. Saha, and F. B. Malik, Phys. Scr. 74, 377 (2006); Phys. Rev A 73, 052703; M. A. R. Patoary, M. A. Uddin, A. K. F. Haque, M. Shahjahan, A. K. Basak, M. R. Talukdar and B. C. Saha, Int. J. Quan. Chem (in press). Supported by NSF CREST. [Preview Abstract] |
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Y1.00040: Electron impact ionization of ground and metastable states of Ag, Au and Cu M.A. Ali, P.M. Stone Direct ionization cross sections of metal atoms by electron impact are needed data for plasma physics, gas discharges and atmospheric physics. We present ionization cross sections of the ground states of silver, gold and copper calculated within the Binary-Encounter-Bethe (BEB) model of Kim and Rudd [1]. These are compared with available experimental data for silver and copper [2], very scant and old data for gold and discordant data for copper [3] and the theoretical Plane-Wave-Born [4] and non-relativistic one electron calculational results. We also investigate the importance of ionization from the metastable state of copper for the total direct ionization. [1] Y-K. Kim and M. E. Rudd, Phys. Rev. A \textbf{50 }3954 (1994). [Preview Abstract] |
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Y1.00041: Cross Sections for Electron Scattering from $Fe^{11+}$ Ions Swaraj Tayal The B-spline Breit-Pauli R-matrix method is used to investigate electron impact excitation of allowed and forbidden transitions in $Fe^{11+}$ in the energy range from threshold to 12.0 Ryd. The relativistic effects are adequately accounted for by using directly fine-structure close-coupling expansions. The multiconfiguration Hartree-Fock method with term-dependent non- orthogonal orbitals is employed for an accurate representation of the target states. The non-orthogonal orbitals allowed us to optimize the atomic wave functions for different target states independently, resulting in more accurate target descriptions than those used in the previous collision calculations. The calculated excitation energies are in excellent agreement with the experimental values. We performed three independent electron scattering calculations by including 41 levels, 90 levels, and 104 levels in the close coupling expansion to check the convergence of results. The distinctive feature of the method is the use of B-splines as a universal basis to represent the scattering orbitals in the inner region. Only limited orthogonality conditions to the continuum orbitals are imposed. The oscillator strengths and cross sections for several transitions will be presented. [Preview Abstract] |
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Y1.00042: ATOMIC PHOTOIONIZATION AND PHOTODETACHMENT PROCESSES |
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Y1.00043: The New On-Line Photoionization Spectrometer at FLASH Pavle Juranic, Michael Martins, Lorenz Jahn, Susanne Bonfigt, Stephan Klummp, Jens Viefhaus, Kai Tiedtke Due to the stochastic nature of the SASE process and the resulting pulse-to-pulse fluctuations of the Free-electron Laser (FEL) photons, the experimenters require the knowledge of the properties of the beam they're working with. In particular, the experimenter who is investigating narrow atomic or molecular resonances, phase transitions, or any other kind of effect heavily dependent on the photon energy of an FEL would need to know the precise photon energy of each individual photon bunch. Real-time photon energy measurement could also be used by the operators of the FEL machine to tune the beam. Also, whatever spectrometer used must not interfere with the beam so significantly to cause the experiment to receive substantially less light, degrading the quality the beam's wavefront, coherence, pulse length, and other properties. The group at the Free Electron Laser in Hamburg (FLASH) has developed an on-line photoionization spectrometer that uses electron and ion time of flight (TOF) spectrometers and gases as a way to measure the photon pulse energy. By measuring the out-of-focus-beam electron kinetic energy spectra, and by looking at the relative ion signal photoionization ratios of already known noble gases, one can determine the photon energy of the FEL beam. [Preview Abstract] |
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Y1.00044: Inner-shell photoionization of atomic chlorine near the 2p$^{-1 }$ edge: a Breit-Pauli R-matrix calculation Z. Felfli, N.C. Deb, S.T. Manson, A. Hibbert, A.Z. Msezane An R-matrix calculation which takes into account relativistic effects via the Breit-Pauli (BP) operator is performed for photoionization cross sections of atomic Cl near the 2p threshold. The wavefunctions are constructed with orbitals generated from a careful large scale configuration interaction (CI) calculation with relativistic corrections using the CIV3 code of Hibbert [1] and Glass and Hibbert [2]. The results are contrasted with the calculation of Martins [3], which uses a CI with relativistic corrections, and compared with the most recent measurements [4]. [1] A. Hibbert, \textit{Comput. Phys. Commun. }\textbf{9, }141 (1975) [2] R. Glass and A. Hibbert, \textit{Comput. Phys. Commun. }\textbf{16, }19 (1978) [3] M. Martins, J. Phys. B \textbf{34}, 1321 (2001) [4] D. Lindle \textit{et al} (private communication) Research supported by U.S. DOE, Division of Chemical Sciences, NSF and CAU CFNM, NSF-CREST Program. Computing facilities at Queen's University of Belfast, UK and of DOE Office of Science, NERSC are appreciated. ~ [Preview Abstract] |
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Y1.00045: Infra-red Photodetachment of Lanthanide Anions K.C. Chartkunchand, V.T. Davis, S.S. Duvvuri, Z.A. McCormick, J.S. Thompson, P.P. Wiewior, Aaron Covington Lanthanide anions, including Lu$^{-}$ and Tb$^{-}$, have been investigated at 1030 nm using a crossed laser-ion beams Laser Photodetachment Electron Spectroscopy apparatus. In the case of Lu$^{-}$, the measured spectral variation of the asymmetry parameter is shown to be consistent with $p$-subshell photodetachment using the simplified model of Hanstrop $et. al$ [Phys. Rev. A 40, 670 (1989)]. The experimental results are shown to be in good agreement with the bound states predicted by Elliav $et. al$ [Phys. Rev. A 52, 291 (1995)] and are in excellent agreement with the more recent calculations O'Malley and Beck [Private Communication 2008]. Results of recent photodetachment experiments on Tb$^{-}$ are also presented. which extend previous measurements to lower photon energies. [Preview Abstract] |
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Y1.00046: Inner-shell photodetachment from Se$^{-}$ N.D. Gibson, C.W. Walter, R.L. Field III, D.J. Carman, J.Z. Shapiro, R.C. Bilodeau, I. Dumitriu, N. Berrah, A. Aguilar The photodetachment spectrum of Se$^{-}$ from 50 - 62 eV has been investigated using the merged ion-photon beam photodetachment technique. Se$^{- }$ions were produced in a Cs sputtered negative ion source (SNICS II) while the photons were produced by the undulator on the Advanced Light Source Ion-Photon Beamline 10.0.1. Se$^{+ }$and$^{ }$Se$^{++}$ ions formed by double and triple detachment were detected as a function of photon energy. Correlations in short-lived negative ion resonances formed by completely filling the valence 4$p $shell in Se$^{-}$ by photoexcitation of 3$d $electrons lead to three resonance structures. The resonances are observed in both the Se$^{+ }$and$^{ }$Se$^{++}$ decay channels bound by several eV below the 3$d$ detachment threshold near 54 eV. [Preview Abstract] |
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Y1.00047: Inner-Shell Photodetachment Thresholds of Transition Metal Negative Ions Ileana Dumitriu, R.C. Bilodeau, T.W. Gorczyca, C.W. Walter, N.D. Gibson, A. Aguilar, Z. Pesic, D. Rolles, N. Berrah Inner-shell photodetachment threshold studies of transition metal negative ions in Fe- and Ru- have been conducted using the merged ion-photon beam technique at the Advanced Light Source beamline 10.0.1. The ions extracted from the SNICS source were mass selected and merged collinearly with the photon beam. Inner-shell photodetachment and subsequent Auger decay produce positive ions which are detected as a function of photon energy. Excitations from p-electrons to open d-shells were carried out in Fe- and Ru-. Our measurements revealed for the first time a d-wave Wigner law in single-photon measurements of negative ions. This work is funded by DOE, office of Science, BES, Chemical Sciences, Geosciences and Biosciences Divisions. NDG and CWW acknowledge support from NSF grant No.0456916 and 0757976. [Preview Abstract] |
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Y1.00048: Promoting a Core Electron to Fill a d-Shell: A Novel Threshold Law and Shape and Feshbach Resonances R.C. Bilodeau, I. Dumitriu, N.D. Gibson, C.W. Walter, N. Berrah Two new results emerging from inner-shell photodetachment of atomic negative ions will be presented, following studies in Pt$^{-}$. First, the d-wave form of the Wigner threshold law is observed for the first time in single-photon measurements. Second, single-vacancy valence shells are filled with a core electron, which would ordinarily be expected to result in stabilization of the core excited state, producing Feshbach resonances. However, we find that stabilization does not occur for some core excitations, dramatically demonstrating the importance of core-valence interactions. [Preview Abstract] |
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Y1.00049: Double Photoionization of Lithium Revisited Ralf Wehlitz, Dragan Luki\'c In a previous paper\footnote{R. Wehlitz, J.B. Bluett , and S.B. Whitfield, Phys. Rev. Lett. {\bf89}, 093002 (2002)} we believed to have seen oscillations in the double-photoionization cross section of lithium. However, a recent investigation revealed that resonances at twice the photon energy (compared to the near-threshold energy region) are more pronounced than had been expected\footnote{R. Wehlitz and P.N. Jurani\'c, Phys. Rev. A {\bf 74}, 042721 (2006)}. This prompted us to revisit the near-threshold region of the lithium double-to-single photoionization ratio. Using a slightly higher energy resolution in a new experiment on the same beamline, we could identify resonances in that ratio due to second-order light. While the second-order light contribution is small, so is the double-photoionization cross section in first-order light near threshold. The ``resonances'' observed near threshold match the inner-shell resonances at twice the photon energy fairly well and can indeed explain the previously seen ``oscillations''. [Preview Abstract] |
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Y1.00050: Single photon double ionization of the He-like Li$^+$ ion B.M. McLaughlin, C.P. Ballance The success of the R-matrix plus pseudo-state (RMPS) method to model single photoionization, is exploited and extended to calculate the single photon double ionization cross-section for the He-like ion, Li$^+$, from both the ground state and the n=2 excited levels. Comparisons of the present R-matrix plus pseudo-state (RMPS) results are made with other theoretical methods such as time-dependent close-coupling (TDCC), the convergent close-coupling (CCC) and the B-spline approach. Suitable agreement between the various theoretical approaches are achieved but some differences occur which are high-lighted and discussed. The maxima in the respective cross sections are extremely small, being in the region of 2Kb for the ground state and 1Kb and 6 Kb, for the n=2 meta stable states which makes their experimental determination very challenging. [Preview Abstract] |
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Y1.00051: Theoretical Study of the Photoionization of Be-like Ions Wei-Chun Chu, Hsiao-Ling Zhou, Steven T. Manson The photoionization for a number of the ions of the Be-like isoelectronic sequence have been studied from the neutral to Z=26 (Fe) using Breit-Pauli $R$-matrix program. The cross sections from ${ }^1S_0^e $ ground state and ${ }^3P_0^o $ metastable state were calculated up to $1s^24f_{7/2} $ threshold of the three-electron final-state ion. The total cross sections for Be and B$^{+}$ are in good agreement with recent measurements. The partial cross sections for the various channels are compared with earlier calculations. The various autoionizing resonances from ground and metastable states were identified and characterized (energy and width) with the QB program [1], and the overlapping of the resonance series is discussed and compared with earlier work. The evolution of the resonances and the nonresonant cross section along the isoelectronic sequence is delineated. This work was supported by DOE and NASA. All calculations were performed on the DOE NERSC system. [1] L. Quigley, K. Berrington, and J. Pelan, Comput. Phys. Commun. \textbf{114}, 225 (1998). [Preview Abstract] |
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Y1.00052: VIBRATIONAL AND ROTATIONAL MOLECULAR COHERENCE |
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Y1.00053: Suppression of O$_{2}^{+}$ dissociation using intense few-cycle pulses M. Zohrabi, B. Gaire, J. McKenna, A.M. Sayler, Nora G. Johnson, E. Parke, K.D. Carnes, I. Ben-Itzhak The dissociation spectra of an O$_{2}^{+}$ beam in an intense 795 nm laser are rich in structure. This is due to the complex laser-driven dynamics involving coupling between the many different electronic states of O$_{2}^{+}$. We employ a coincidence 3D momentum imaging method to unravel these dynamics and reveal the important dissociation pathways. Intriguingly we find that unlike most small diatomic molecules, the dissociation spectra are particulary sensitive to pulse duration with dramatic differences observed between 8 and 40 fs pulses. We trace the enhancements of some channels and suppression of others for various pulses back to the femtosecond dynamics which dictate the dissociation pathways involved. [Preview Abstract] |
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Y1.00054: Asymmetric fragmentation of D$_{2}$H$^{+}$ by intense ultrashort laser pulses J. McKenna, A.M. Sayler, B. Gaire, Nora G. Johnson, K.D. Carnes, B.D. Esry, I. Ben-Itzhak The triatomic hydrogen molecular ion is a fundamentally important molecule as it plays a key role in interstellar and plasma chemistry. More importantly for intense laser studies, it is seen as the stepping stone to better understanding the laser-driven dynamics of polyatomic molecules. Recently, we have made a breakthrough by performing the first studies on H$_{3}^{+}$ and D$_{3}^{+}$ fragmentation in ultrashort intense laser pulses using coincidence 3D momentum imaging. Studying the D$_{2}$H$^{+}$ isotopologue, we now find exciting differences between equivalent breakup channels. For example, for 7\,fs, 790\,nm pulses the 2-body single ionization channel, H$^{+}$+D$_{2}^{+}$, is a factor of 5 larger than its counterpart channel, D$^{+}$+HD$^{+}$. Wavepacket propagation calculations are needed to determine the precise origin of the effect. [Preview Abstract] |
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Y1.00055: Multiple ionization and fragmentation of diatomic molecular ions in intense ultrashort laser pulses B. Gaire, J. McKenna, Nora G. Johnson, A.M. Sayler, E. Parke, K.D. Carnes, I. Ben-Itzhak Studies on small diatomic molecules benefit our understanding of laser-molecule interactions. Traditionally experiments are performed on neutral gas-phase targets. To create diversity, we have studied the ionization and fragmentation of several diatomic molecular ions (N$_{2}^{+}$, CO$^{+}$, NO$^{+}$, and O$_{2}^{+})$ in intense (up to 5$\times $10$^{15}$ W/cm$^{2})$ ultrashort (8 and 40 fs), 790 nm laser pulses. Coincidence 3D-momentum imaging is employed to separate and obtain the kinematics of all the breakup channels. The measured kinetic energy release and the angular distributions of the breakup processes suggest that the multi-electron dissociative ionization (MEDI) of molecules is a ladder-like process, where the molecules stretch prior to each ionization step in a sequential manner. This behavior is consistent with some earlier studies that use neutral molecules as targets. [Preview Abstract] |
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Y1.00056: Strong Field Ionization of Ne$^{n+}$(n$<$=3) for an Ultrafast, 400 nm Laser Field Bruce L. Wen, Nagitha Ekanayake, Jane Waesche, Samantha White, Adam Watts, Teddy Stanev, Barry C. Walker Total ionization yields are reported for neon (Ne$^{+}$ to Ne$^{3+}$ at intensities from 10$^{14}$ W/cm$^{2}$ to 10$^{17}$ W/cm$^{2}$ for a 400 nm laser field. Sequential ionization processes are modeled by tunneling ionization and shown to be accurate within a factor of two near saturation for Ne$^{+}$ and Ne$^{2+}$. Non-sequential multi-electron ionization is observed for the ionization yield of Ne$^{2+}$ and Ne$^{3+}$. The ratio of ion yields from 800 nm and 400 nm laser fields for neon charge states for Ne$^{2+ }$and Ne$^{3+}$ show non-sequential ionization for a 400 nm laser field is different when compared to that for an 800 nm laser field. A semi-classical, 3D relativistic rescattering model is compared to the data. [Preview Abstract] |
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Y1.00057: Time--resolved Laser Coulomb Explosion Imaging of N$_{2}$, O$_{2}$ and CO molecular dynamics Irina Bocharova, Igor Litvinyuk, Lewis Cocke, Sankar De, Ray Dipanwita, Magrakvelidze Maia, Predrag Ranitovic We studied dissociation dynamics of nitrogen, oxygen and carbon monoxide molecules following their interaction with intense few-cycle laser pulse. Time-resolved Laser Columb Explosion Imaging (TLCEI), a pump-probe technique, was employed to measure kinetic energy release of correlated explosion fragment as a function of time delay for symmetric and assymetric break-up channels. Kinetic energy release intensity map reflects the time behavior of parts of a nuclear wave packet oscillating in potential wells and moving along unbound potential curves of many molecular ion states. Assuming experimental conditions (intensity, pulse duration) and tunneling ionization mechanism we were able to built simple classical and quantum models uncovering details of dissociation process for N$_{2}$, O$_{2}$, CO molecules which fit perfectly our experimental results. [Preview Abstract] |
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Y1.00058: Electron-ion momentum coincidence experiments on hydrogen molecules dissociated by intense femtosecond laser pulses M. Magrakvelidze, S. De, F. He, I. Bocharova, D. Ray, U. Thumm, I. Litvinyuk We report two experiments on D$_{2}$ using electron-ion coincidence momentum spectroscopy in COLTRIMS. In both experiments we measure electron momentum in coincidence with momentum of one D$^{+}$ ion. In the first one we used 50 fs circularly polarized pulses of 1850 nm wavelength to measure angular anisotropy of tunneling ionization. By measuring the relative angle between an ionized electron and deuteron we deduce the angular dependence of the molecular ionization probability without aligning the molecules first. With 2$\times $10$^{14}$ W/cm$^{2}$ pulse intensity neutral D$_{2}$ molecules are 1.15 times more likely to be ionized when the laser electric field is parallel to the molecular axis than for the perpendicular orientation. This is in excellent agreement with our theoretical model which is based on solving the time dependent Schr\"{o}dinger equation in the velocity gauge. In the second experiment, we used pump-probe technique with two few-cycle 800 nm pulses separated by variable time delay. Neutral molecule is singly ionized with a weak pump pulse and then is exploded by a stronger probe pulse. The fragments of the reaction are detected in coincidence at various time delays. Gating the electron energy spectra on pump-probe delays and kinetic energies of D$^{+}$ we observe an evolution of these spectra indicative of changing electronic structure of the D$_{2}^{+}$ ion. [Preview Abstract] |
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Y1.00059: Molecular-orientation-dependent ac Stark effect and its impact on multiphoton processes Xi Chu We study the dependence of the AC Stark shifts of electronic energies on the molecular orientation relative to the polarization direction of an incident intense laser field, using a three dimensional non-Hermitian Floquet method and H$_2^+$ as a model system $^{[1]}$. Simultaneously, we also study the orientation dependent high harmonic generation (HHG) and multiphoton ionization (MPI). We find that with the presence of near-one-photon resonance, the Stark effect strongly mixes electronic states of different symmetries to create quasienergy states (QESs). The orientation dependence of multiphoton processes, in which these QESs play an important role, becomes complex. Population transfer is better achieved with aligned molecules and optimized orientation. When the energies of emitted photons are lower than the ionization energy, the Stark effect plays an important role in the orientation dependence of HHG intensity and polarization. It also is important for MPI, when the Keldysh parameter is larger than one. Results from fixed-nuclei calculations for a series of internuclear distances are used to obtain values for different vibrational states. With a multiphoton resonance, the HHG intensity of the fixed-nuclei model resembles that of the lowest vibrational state. Molecular vibration of H$_2^+$ has a great effect in MPI and the off-resonant HHG. [1]~X. Chu, Phys. Rev. A {\bf 78}, 043408 (2008). [Preview Abstract] |
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Y1.00060: Manipulating the torsion of molecules by strong laser pulses Christian Bruun Madsen, Lars Bojer Madsen, Simon Stenfeldt Viftrup, Mikael Peter Johansson, Thomas Bj{\O}rnskov Poulsen, Lotte Holmegaard, Vinod Kumarappan, Karl Anker J{\O}rgensen, Henrik Stapelfeldt The manipulation of molecules by strong laser pulses has attracted much attention. Specifically, non-resonant laser fields apply torques on molecules, due to the interaction between the induced dipole moment and the laser field itself. This induced polarizability interaction has proven very useful for controlling the alignment of molecules with respect to the laser polarization. I will present the first efforts made to extend the methods of alignment to manipulating the torsion in a molecule. I will consider the laser induced dynamics of the two phenyl rings of a biphenyl molecule. The present work demonstrates that strong-field laser physics methods and time-resolved measurements are not limited to small linear molecules, but can actually be useful for studying exciting fundamental phenomena in larger complex systems. I will show both experimental and theoretical results. [Preview Abstract] |
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Y1.00061: New determination of the structure parameters in the molecular tunneling ionization model Song-Feng Zhao, Cheng Jin, Anh-Thu Le, Chii-Dong Lin Molecular ADK model (MO-ADK) [1] has been successfully used to study the ionization of molecules in recent years. However, there is indication that the model does not predict the correct alignment dependence of the ionization rates for CO$_{2}$ molecules [2]. In the MO-ADK model, the wavefunction of the highest-occupied orbital at large distance is needed in the tunneling region. The wavefunction calculated using the quantum chemistry code usually is not accurate at large distance. In this work, we re-examined the MO-ADK model where the HOMO wavefunction are calculated using B-splines functions in the one-center expansion. Results from the MO-ADK models for several molecules will be presented and compared to those from other ab initio calculations whenever available. [1] X. Tong et al, Phys. Rev. A {\bf 66}, 033402(2002). [2] D. Pavicic et al, Phys. Rev. Lett. {\bf 98}, 243001 (2007). [Preview Abstract] |
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Y1.00062: Quantum-beat imaging of the nuclear dynamics in D$_{2}^{+}$: Dependence of bond softening and hardening on laser intensity, wavelength, and pulse duration Maia Magrakvelidze, Feng He, Thomas Niederhausen, Igor Litvinyuk, Uwe Thumm Based on a quantum mechanical model, we calculate the time evolution of an initial nuclear vibrational wave packet in D$^{+}_{2}$ generated by the rapid ionization of D$_{2}$ in an ultrashort pump-laser pulse. By Fourier transformation of the nuclear probability density with respect to the time delay between the pump pulse and the wave packet's instant destructive Coulomb explosion imaging at the high-intensity spike of an intense probe-laser pulse, we provide two-dimensional, internuclear distance (R) dependent power spectra that serve as a tool for visualizing and analyzing the nuclear dynamics in D$^{+}_{2}$ in an intermittent external laser field. The external field models the pedestal to the central ultra-short spike of a realistic probe pulse. Variation of the intensity, wavelength, and duration of this probe-pulse pedestal, allows us to identify optimal laser parameters for the observation of field-induced bond softening (BS) and bond hardening (BH) in D$^{+} \quad _{2}$ and suggests a scheme for quantitatively testing the validity of the Floquet picture that is commonly used for the interpretation of short-pulse laser-molecule interactions. [Preview Abstract] |
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Y1.00063: Extraction of Electron Above-Threshold-Ionization Spectra from Core Region of Time-Dependent Wave Packet Dmitry Telnov, Shih-I Chu We present a new method for accurate calculations of electron energy and angular distributions after above-threshold multiphoton ionization. The procedure does not require propagation of the wave packet at large distances since the electron spectra are extracted from the vicinity of the atomic core. The method is based on the extension of the Kramers--Henneberger picture of the ionization process while the final expressions involve the wave function in the laboratory frame only. The approach is illustrated by a case study of above-threshold ionization of the hydrogen atom subject to intense laser pulses with the wavelength 800 nm. The ejected electron energy and angle distributions have been calculated and analyzed for long (20 optical cycles) as well as short (4 optical cycles) laser pulses. We explore the electron spectra dependence on the duration of the laser pulse and carrier-envelope phase (CEP). In particular, we predict a non-zero CEP-dependent total momentum gained by the electrons as a result of the interaction with the laser pulse. [Preview Abstract] |
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Y1.00064: ELECTRON-MOLECULE COLLISIONS |
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Y1.00065: Electron induced bond-breaking at low energies in HCOOH and Glycine: The role of very short-lived $\sigma^*$ anion states Ilya Fabrikant, Paul Burrow, Gordon Gallup Cross sections for dissociative electron attachment (DEA) to formic acid and glycine are calculated by the resonant R-matrix theory. A model with one effective reaction coordinate close to the O-H stretch motion is employed. The choice of the anion R- matrix pole and the surface amplitude as functions of the reaction coordinate for formic acid are based on scattering phase shift calculations using the finite element discrete model. For glycine the input parameters are adjusted to reproduce experimental data. The results show that the mechanism of DEA in these molecules is similar to that for the hydrogen halides and involves electron capture into a $\sigma^*$(OH) orbital, so that no $\sigma^*/\pi^*$ coupling is required. Nonlocal effects play an important role for both molecules. In particular, pronounced steps and cusps are seen at the vibrational excitation thresholds. A sharp threshold peak in glycine is interpreted as a vibrational Feshbach resonance. [Preview Abstract] |
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Y1.00066: VUV Study of Electron Impact Dissociative Excitation of H$_{2}$S Stephen Brotton, Wladek Kedzierski, William McConkey The dissociative excitation of H$_{2}$S following electron impact has been studied in the electron energy range from threshold to 300 eV . H, S and S$^{+}$ emissions in the 90 to 170 nm region have been identified and quantified. The dominant Lyman-$\alpha $ feature at 121.6 nm has a measured emission cross section of (9.79 $\pm $ 0.67) x 10$^{-18}$ cm$^{2}$ at 100 eV. This was used to normalize 100 eV cross sections for all observed spectral features. Excitation functions of the dominant H and S emissions have been studied with particular emphasis on the near-threshold region. A number of dissociation channels have been identified. [Preview Abstract] |
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Y1.00067: Dissociative Ionization of $BF_3$ and its fragments Milka Nikolic, Marija Raskovic, Svetozar Popovic, Leposava Vuskovic Dominant contribution of particular molecular orbitals to the individual fragment production exists, in some cases, in the dissociative ionization by electron impact [1]. We have calculated the electron-impact ionization rates of $BF_3$ and its fragments. In our calculation electronic structures of $BF_3$ and its fragments were described with several empirical basic sets. After geometry optimization using density functional method B3LYP, MO parameters were calculated with UHF, CCSD(T) and OVGF methods [2]. Electron-impact ionization cross-sections were calculated employing the Binary-Encounter-Bethe approximation and results were compared with available experimental data. In the absence of clear-cut assignment, the fractional MO-fragment correlation was made using geometry considerations. As the final test of the method, we compared the ionization rates for electron energy distribution present in sheath mode of the repetitively pulsed d.c. diode system with those obtained experimentally. \\ \newline [1] S. Popovic, S. Williams, and L.Vuskovic, Phys. Rev. A 73, 022711, (2006). \newline [2] Y-K Kim, K. K. Irikura, AIP conferences proceedings 543, 220 (2000). [Preview Abstract] |
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Y1.00068: Dissociative electron attachment to CF$_3$Cl: inclusion of two vibrational modes M. Tarana, P. Wielgus, S. Roszak, I.I. Fabrikant We present a study of multimode effects in dissociative electron attachment to CF$_3$Cl molecules using a time-independent version of the local complex potential theory. Symmetric stretch C-Cl vibrations $\nu_3$ and symmetric deformation (or so-called ``umbrella") vibrations $\nu_2$ are included. The neutral and anion potential energy surfaces are calculated using the second-order Moller-Plesset perturbation theory with an empirical adjustment of the vertical attachment energy. The final-state vibrational distribution in the CF$_3(\nu_2)$ fragment is dominated by the $\nu_2=2$ state. We also find an increase of the total cross section as compared to one-dimensional calculations. This is explained by an increase of the anion survival probability. [Preview Abstract] |
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Y1.00069: Dissociative Electron Attachment to HCCH, HCN/HNC and HCCCN Slim Chourou, Ann Orel Previous work on the dissociative electron attachment (DEA) to acetylene, hydrogen cyanide and its isomer and cyano-acetylene shows that the dissociation process for these systems is inherently polyatomic. We present a comparative summary of the study of these species believed to play a role in the chemistry of interstellar media and to present key elements in the prebiotic synthesis in early Earth. Our treatment was carried out in the low energy range (0-6 eV for HCCH and HCN/HNC and 0-12 eV for HCCCN) using a suitable coordinate system that allows taking into account distortions in the symmetry of the polyatomic target molecule. We have performed electron scattering calculations using Complex Kohn Variational method to determine the low-lying shape resonance energies and autoionization width for various geometries of these molecules. The resonance parameters are then used to construct the complex potential energy surfaces relevant to the metastable negative ion formed in each case. The nuclear dynamics is performed using the Multiconfiguration Time-Dependent Hartree (MCTDH) approach and the flux of the propagating wavepacket is used to compute the DEA cross section associated with the dissociation channels addressed for each system. The computation results are then compared to the available experimental results. [Preview Abstract] |
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Y1.00070: O$^{-}$ channels of Dissociative Electron Attachment to water and heavy water molecules Hidehito Adaniya, Benedikt Rudek, Timur Osipov, Sun Lee, Thorsten Weber, Marcus Hertlein, Markus Schoeffler, Mike Prior, Ali Belkacem A COLTRIM technique is modified to measure the kinetic energy and angular distribution of O$^{-}$ ions arising from dissociative electron attachment to water and heavy water molecules. A low energy pulsed electron, an effusive water target, a pulsed extraction plate are used in combination with the COLTRIMS spectrometer. The spectrometer carries an electrostatic lens system to compensate the effusiveness of the target. This technique is applied to study the O$^{-}$ channels in the three Feshbach resonances of water and heavy water anion. The measured kinetic energy release will give the energy partitioning among the fragments, and the means to identify the two-body and three-body breakup channels. The angular distribution of the O$^{-}$ ions with respect to the electron beam is found to reflect well the breakup dynamics of the H$_{2}$O$^{-}$ at the dissociation. The experimental results are compared with the theoretical predictions. [Preview Abstract] |
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Y1.00071: Calculations of cross sections data for scattering of electrons on BF3 Marija Vranic, Marija Radmilovic-Radjenovic, Zoran Lj. Petrovic, Hemal N. Varambhia, Jonathan Tennyson In recent years there has been a need to establish extensive databases of atomic and molecular collisional cross sections. Boron trifluoride is used as a dopant in ion implantation, for initiating polymerisation of unsaturate compounds, as a catalyst in isomerization, alkylation, esterification, condensation, and is used in sensitive neutron detectors. This work dealing with BF3 is focused on computing the total (integrated) and excitation electron scattering cross-sections by using the R-matrix method. This data will enable a more accurate calculation of the transport coefficients. The R-Matrix code Quantemol-N has been used for the calculations. The basis set used in this calculation was 6- 311G, and the method was CI (Configuration Interaction). The computed total and BEB ionization cross sections were compared to known experimental studies. The results indicate the presence of a shape resonance of symmetry B1 (A2'' in D3h) at around 4.5 eV. [Preview Abstract] |
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Y1.00072: MATTER WAVE INTERFEROMETRY |
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Y1.00073: Towards a Gyroscope with a Large Interferometer Area, Testing the Fundamentals of Physics Franck Michaud, Thomas Leveque, Arnaud Landragin After having investigate the limits of our previous inertial sensor using a cold atom interferometer of caesuim in the all six axis of inertia [1], we project to built a brand new second and better version of interferometer, in order to improve the high accuracy and to be able to do some testing of fundamental physics (atomic neutrality, Aharonov-Bohm effect, electric polarisability) [2]. The new gyroscope will stand at 1 meter high, with a large sensing area and interrogation time. We expect also to use large momentum transfer beam splitter [3]. More details of the experiment under construction will be given.\\[3pt] References:\\[0pt] [1] Six axis Inertial Sensor Using Cold Atom Interferometry, B. Canuel and al, Phys. Rev. Lett. 97, 010402 (2006)\\[0pt] [2] How to test Atom and Neutron Neutrality with Atom Interferometry, A. Arvanitaki and al, Phys. Rev. Lett. 100, 120407 (2008)\\[0pt] [3] Atom Interferometry with up to 24-Photon-Momentum-Transfer Beam Splitters, H. M\"{u}ller and al, Phys. Rev. Lett. 100, 180405 (2008) [Preview Abstract] |
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Y1.00074: Decoherence of a Rb BEC caused by stray magnetic fields and surface effects Arne Schwettmann, Jonathan Tallant, Donald W. Booth, C. Erin Brown, James P. Shaffer We present progress and perspectives on measuring the influence that stray magnetic fields and surface effects have on the decoherence of a BEC in a double-well potential surface trap. The double-well trapping potential is provided by a radiofrequency magnetic microtrap that traps Rb with trap minima located $\sim $100 $\mu $m from the surface of an atom chip. The coupling to the environment is from surface effects generated by the atom chip and through an applied fluctuating magnetic field. The spectral noise density of the applied magnetic field is varied in order to investigate the effects of subohmic, superohmic and ohmic type baths on the decoherence rate. \newline [Preview Abstract] |
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Y1.00075: New guiding structures for atom interferometry with cold atoms Alexey Tonyushkin, Mara Prentiss We demonstrate new magnetic guides for cold atoms suitable for atom interferometry experiments. These guides are based on macroscopic copper tape coils that allow the guide to be located more than a cm above the surface of the coils. Thus, unlike micro-chip structures that require that the atoms be very close to the surface of the chip, these structures can be placed outside the vacuum chamber. The large operational distance reduces decoherence due to waveguide imperfections. This distance is comparable to the one previously achieved with ferromagnetic guide; however, the new guides offer precise control over the magnetic field, though they do require relatively high current. The guides with two different geometries are developed based on such coils, where in one case the atoms are located above the coils and in the other case the atoms are located symmetrically between the coils. The symmetrical version of the guide has a much lower magnetic field curvature than the other macroscopic guides have. The guides can also be used for nonlinear optics experiments with cold atoms. [Preview Abstract] |
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Y1.00076: Enhancement of the Sagnac rotational phase shift in a coherently coupled array of atom interferometers Christopher Search, John Toland, Marko Zivkovic The ability to interferometrically detect inertial rotations via the Sagnac effect has been a strong stimulus for the development of atom interferometry because of the potential ${10}^{10}$ enhancement of the rotational phase shift in comparison to optical Sagnac gyroscopes. Here we analyze ballistic transport of matter waves in a one dimensional chain of N coherently coupled quantum rings in the presence of a rotation of angular frequency $\Omega$. We show that the transmission probability T, as a function of the rotation rate, exhibits zero transmission stop gaps interspersed with regions of rapidly oscillating finite transmission. With increasing N, the transition from zero-transmission to the oscillatory regime becomes an increasingly sharp function of $\Omega$ with a slope $\delta T /\delta \Omega \sim N^2$. The steepness of this slope dramatically enhances the response to rotations in comparison to conventional single ring interferometers such as the Mach-Zehnder and leads to a phase sensitivity well below the standard quantum limit. The universality of our transfer matrix approach implies that the results are also applicable to the study of the Sagnac effect in ballistic conductors (such as graphene and two dimensional electron gases). [Preview Abstract] |
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Y1.00077: Design and construction of condensate interferometers for inertial navigation applications Robert Horne, John Burke, Jiraphat Tiamsuphat, Vanessa Leung, Cass Sackett Atom interferometry using Bose-Einstein condensates has the potential to be useful for applications in inertial navigation. However, although condensate interferometers have already been demonstrated [1,2] to be feasible as navigation devices, their sensitivity must be improved by increasing their measurement time and arm separation. In previous work we have shown that the sensitivity of interferometers based on atoms confined in a magnetic waveguide are currently limited by residual magnetic field variation along the axis of the guide. We are implementing a linear guide in which such variations are reduced and overall vibration and field stabilization improved. Furthermore, we have also begun constructing a new apparatus in which our design has been extended to a ring configuration. This would enable high-sensitivity gyroscopic measurements of rotation. In our poster we will present our latest results on both interferometers. [1] Y.J. Wang \textit{et al}., ``Atom Michelson interferometer on a chip using a Bose-Einstein condensate.'', \textit{Phys. Rev. Lett}. \textbf{94} 090405 (2005). [2] O. Garcia \textit{et al}., ``Bose-Einstein condensate interferometer with macroscopic arm separation.'', \textit{Phys. Rev. A} \textbf{74} 031601(R) (2006). [Preview Abstract] |
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Y1.00078: Single Electron Double Slit Experiment and Wide Angle Beam Splitter Scot McGregor, Roger Bach, Adam Caprez, Herman Batelaan, Kayvan Aflatooni, Damian Pope We present our work on a double slit experiment for single electrons. In this experiment an electron interference pattern is recorded one electron at a time. Similar experiments have been done for single electron interference patterns, but never before has this been done for a true double slit. Our experiment is to be included in a documentary about quantum mechanical interference, which is being made by the Perimeter Institute and will be made available to quantum mechanics instructors. We also present data from our wide angle electron beam splitter. The beam is split by a nanofabricated grating after which a M\"{o}llenstedt biprism allows for further separation of the diffraction orders. With this beam splitter a beam separation of one centimeter is reached at the detection plane. Difficulties are discussed in the development of this beam splitter as well as the possibility of using such a beam splitter in a large area electron interferometer. [Preview Abstract] |
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Y1.00079: Random Electrodynamics, the Harmonic Oscillator and Electron Diffraction Cheng-Wei Huang, James Strohaber, Herman Batelaan In the Kapitza-Dirac effect the mechanism by which the electron exchanges momentum with the light grating is stimulated Compton scattering. However, it is unknown by which mechanism electrons exchange momentum when diffracting from a material grating.$^{1}$ We are studying mechanism by which momentum could be exchanged. One such mechanism is based on vacuum field interactions. A full QED calculation has never been performed for either the KD-effect or diffraction from a material grating, and is considered very hard to do. Therefore, we use the semi-classical theory of Random Electrodynamics (RED). To test our capability to describe the vacuum field appropriately with RED, we apply it to the ground state of the harmonic oscillator. We find a Gaussian probability distribution that satisfies the Heisenberg uncertainty principle. Progress towards applying RED to excited states and diffraction from gratings will be reported. 1. H. Batelaan. Rev. Mod. Phys. 79, 929 (2007) [Preview Abstract] |
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Y1.00080: QUANTUM AND/OR NONLINEAR OPTICS |
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Y1.00081: Phase conjugation of Laguerre-Gaussian beams by stimulated Brillouin scattering Aaron Seidel, Matthew Bigelow Methods of inexpensively and efficiently converting a Gaussian beam into a Laguerre-Gaussian (LG) beam are explored in an effort to observe the phase conjugation of a LG beam by stimulated Brillouin scattering. Stimulated Brillouin scattering is a non-linear process that occurs when an intense electric field, in the form of a laser, passes through a susceptible medium resulting in over 90\% of the incident beam being back scattered or reflected. LG beams have a vortex or doughnut shape with the photons carrying integer values of orbital angular momentum. In this work different bleaching solutions are applied to film containing images of computer-generated holograms to optimize the transformation of a Gaussian into a LG beam. After observing stimulated Brillouin scattering with the LG beam, the backscattered beam will be analyzed to detect if orbital angular momentum of the backscattered beam is reversed. [Preview Abstract] |
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Y1.00082: Non-Linear Interactions in Atomic Pump-Probe Optical Phenomena Verne Jacobs Reduced density matrix descriptions are developed for pump-probe optical phenomena in atomic systems, taking into account atomic collisions as environmental phenomena. Time-domain (equation-of-motion) and frequency-domain (resolvent- operator) formulations are developed in a unified manner. In a semiclassical perturbative treatment of the electromagnetic interaction, compact Liouville-space operator expressions are derived for the linear and the general (n'th order) non-linear electromagnetic-response tensors. These expressions are valid for coherent atomic excitations and for the full tetradic-matrix form of the collision operator in the Markov approximation. [Preview Abstract] |
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Y1.00083: Bichromatic Stationary Light Pulses in Cold Atomic Media Yen-Wei Lin, Wen-Te Liao, Thorsten Peters, Hung-Chih Chou, Hung-Wen Cho, Jian-Siung Wang, Pei-Chen Kuan, Ite A. Yu We study the creation of stationary light pulses (SLPs), i.e., light pulses without motion, in cold atoms. Based on the effect of electromagnetically induced transparency, the SLPs are formed via the retrieval of stored probe pulses with two counter-propagating coupling fields. Because of this counter- propagating excitation scheme there exist Raman transitions that create spatially rapidly oscillating ground-state coherences. While for room-temperature or hot media these coherences are negligible due to the atomic motion, we show that they are non-negligible in cold media and prohibit a SLP formation. We experimentally demonstrate a method to suppress these Raman excitations and realize SLPs in laser-cooled atoms. Furthermore, we present a more general explanation for the formation of SLPs, namely several balanced four-wave mixing processes sharing the same ground-state coherence. To demonstrate this new concept we report the first experimental observation of a bichromatic SLP at wavelengths for which no Bragg grating can be established. Our work opens the way to SLP studies in cold as well as in stationary atoms and provides a new avenue to low-light-level nonlinear optics. This work was supported by the NSC Grants No. 95-2112-M-007-039-MY3 and No. 97-2628-M-007-018. [Preview Abstract] |
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Y1.00084: Diffuse light scattering in a ultracold $^{87}$Rb gas under conditions of electromagnetically induced transparency R. Olave, A. Win, I.M. Sokolov, D.V. Kupriyanov, M.D. Havey We report experimental progress in studies of the time-dependence of the intensity of light scattered from an ultracold $^{87}$Rb atomic sample under conditions of electromagnetically induced transparency. For these circumstances, the scattered light intensity depends on the spectral portion of the probe beam within the EIT window. For the diffusely scattered probe radiation in the vicinity of the EIT window, the light transport and scattering properties are also modified. In these experiments, the $^{87}$Rb sample contains about 2 x 10$^{7}$ atoms and is well-described by a Gaussian radius of 0.26 mm and a corresponding optical depth of about 7. We report and discuss experimental results on the temporal, spectral, and polarization characteristics of the total non-forward-scattered light intensity. [Preview Abstract] |
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Y1.00085: Quantum interference in two-photon excitation of the 6s - 7s transition in atomic cesium C. VanDam, A. Hankin, A. Sieradzan, M.D. Havey We report measurements of the relative transition amplitudes for the hyperfine components in the two-quantum 6s $^{2}S_{1/2} \to 7s ^{2}S_{1/2}$ transition of atomic cesium. Two independently-tuned diode lasers, operating at wavelengths around 852 and 1470 nm, are used to induce excitation in warm cesium vapor. Relative probabilities for transitions between specific initial and final hyperfine structure levels are determined as a function of the intermediate virtual level detuning from the spectrally-close 6p $^{2}P_{3/2}$ level. Strong quantum interference effects associated with indistinguishable excitation paths are observed. Relative transition probabilities are in general agreement with predictions of a simple model. Observed approximate 1$\%$ deviations require further analysis. [Preview Abstract] |
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Y1.00086: Continuous Wave Rotational Raman Sideband Generation in Deuterium Gas Jonathan Green, Daniel Sikes, Deniz Yavuz We report 140mW of CW rotational Raman sideband power generated in deuterium gas. To our knowledge this is the most optical power generated by using CW rotational Raman scattering. We begin with a 30W CW beam with a wavelength of 1.5 microns. This beam is locked, using the Pound-Drever-Hall technique, to a high finesse cavity ($\textit{F}$ $\sim$ 10,000) filled with $\sim$ .5 atm of D$_{2}$. The beam is very far detuned from the nearest electronic state in deuterium, but in the cavity it is sufficiently powerful to cause the molecules to undergo a rotational Raman transition and generate 140mW of transmitted Stokes radiation. [Preview Abstract] |
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Y1.00087: Direct Measurement of the Cesium 6P$_{3/2}$ Excited State Diffusion Coefficient in Helium Using Degenerate Four-Wave Mixing Techniques Michael Shaffer, Mirela Gearba, Taylor Lilly, Randall Knize Measurements of diffusion coefficients for excited state atoms can prove difficult since the distances traveled prior to decay are relatively short. An analysis using the degenerate four-wave mixing signal as a function of relative angle allows for a direct measurement of excited state diffusion coefficients in alkalis. The results from our investigation of the diffusion coefficients for the 6P$_{3/2}$ excited state of cesium in the presence of a helium buffer gas at various pressures will be presented. [Preview Abstract] |
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Y1.00088: Shaping the Phase of a Single Photon Joerg Bochmann, Holger Specht, Martin Muecke, Christian Noelleke, Stephan Ritter, Eden Figueroa, David Moehring, Gerhard Rempe The phase of an individual photon is not defined and is therefore not detectable. However, phase changes of the electromagnetic field within individual photon wave packets can be observed, e.g. in a two-photon interference experiment [1]. We report on arbitrary phase shaping of photons which can result in non-bosonic behavior of photon pairs, even without prior entanglement [2]. We send single photons emitted from an atom-cavity system through a fiber electro-optical modulator which induces controlled phase changes during the passage of individual photons. Using time-resolved two-photon interference measurements we identify subgroups of photon pairs that show coalescence (Hong-Ou-Mandel effect [3]). However, by appropriate photon phase tuning we can even reverse this effect and observe anti-coalescence. \newline \newline [1] T. Legero et al., Phys. Rev. Lett. \textbf{93}, 070503 (2004) \newline [2] J.-W. Pan et al., Phys. Rev. Lett. \textbf{80}, 3891 (1998) \newline [3] C. K. Hong et al., Phys. Rev. Lett. \textbf{59}, 2044 (1987) [Preview Abstract] |
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Y1.00089: Towards quantum and non-linear optics with buffer-gas cooled atoms and molecules Sofia Magkiriadou, Dave Patterson, Alexey Gorshkov, Alexander Zibrov, Mikhail Lukin, John Doyle We report on our progress towards using buffer-gas cooling to produce cold coherent optical media with high optical depth. Helium buffer gas is used to cool to a few Kelvin a continuous stream of Rb atoms produced in an oven. While the first experimental demonstration will focus on electromagnetically induced transparency in Rb, we envision a variety of applications, ranging from nonlinear and quantum optics to precision measurements, with atomic or molecular species that are much more difficult to cool using other methods. [Preview Abstract] |
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Y1.00090: Nonlinear optics with polar molecules in optical lattices T.S. Bragdon, E.I. Kuznetsova, S.F. Yelin We explore the feasibility of ultracold polar molecules in optical lattices for realization of efficient photon-photon interactions in quantum information processing. Photon-photon interaction is implemented by converting photons into collective molecular excitations using dark-state polaritons via the electromagnetically induced transparency effect. As a result of dipole-dipole interaction between polar molecules in the lattice the polaritons acquire a nonlinear phase shift, which allows one to realize a photonic phase gate. We discuss major decoherence mechanisms, such as decay from symmetric molecular collective excited states, and explore doubly occupied lattices as a means to avoid this difficulty. [Preview Abstract] |
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Y1.00091: Two-photon interference with two (and only two) independent photons Frank King, Margaret Trias, Martin Ligare It is well known that intensity correlation functions can reveal multi-photon quantum interference effects. The simplest treatments of such effects are restricted to single-mode fields and fields with stationary photon statistics. In contrast to these treatments we study a simple model in which two photons are spontaneously emitted by two spatially separated atoms. We track the properties of the two-photon field as a function of space and time, and during the time in which the photons overlap the intensity correlation function exhibits interference. The detailed features of the interference could be observed in experiments with heralded single photons. Considering the space and time dependence of correlations for fields in which there are only two independent photons highlights the distinction between interference in correlations of quantized fields and interference in correlations of analogous classical fields. [Preview Abstract] |
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Y1.00092: ATOMS IN OPTICAL LATTICES |
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Y1.00093: Quantum simulations of lattice models with alkaline-earth atoms Alexey Gorshkov, Victor Gurarie, Michael Hermele, Eugene Demler, Mikhail Lukin, Ana Maria Rey We propose to use alkaline-earth atoms in optical lattices for quantum simulation of models that are beyond the generic Hubbard model and that rely on the interplay between spin and orbital degrees of freedom. In addition to being interesting and rich in their own right, such models may allow generating fundamental insights into the physics of solid-state systems such as transition metal oxides and heavy fermion materials, which exhibit numerous exotic properties including high temperature superconductivity and spin liquid phases. [Preview Abstract] |
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Y1.00094: One Dimensional Transport of Alkaline-Earth Atoms in a Harmonic Potential Michael Feig, Alexey V. Gorshkov, Ana Maria Rey Recently it has been proposed that using the two clock states of alkaline earth atoms with non zero nuclear spin, it is possible to simulate clean Spin-Orbit many-body Hamiltonians [1]. These systems are particularly well suited for implementing atomic analogs of the Kondo Lattice model in which a band of localized spins interacts with a cloud of itinerant fermions. Here we report our investigations on the transport properties of alkaline earth atoms governed by the Kondo Lattice Model in the presence of a harmonic trapping potential. We discuss how the localized spins modify the dipole oscillations of the mobile atoms, which even in the non interacting case are known to violate the generalized Kohn theorem. [1] A. V. Gorshkov et al. Alkaline-earth atoms as few-qubit quantum registers. Arxiv 0812.3660. [Preview Abstract] |
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Y1.00095: Alkaline-earth atoms as few-qubit quantum registers Alexey Gorshkov, Ana Maria Rey, Andrew Daley, Martin Boyd, Jun Ye, Peter Zoller, Mikhail Lukin We propose and analyze a novel approach to quantum information processing, in which multiple qubits can be encoded and manipulated using electronic and nuclear degrees of freedom associated with individual alkaline-earth atoms trapped in an optical lattice. Specifically, we describe how the qubits within each register can be individually manipulated and measured with sub-wavelength optical resolution. We also show how such few-qubit registers can be coupled to each other in optical superlattices via conditional tunneling to form a scalable quantum network. Finally, potential applications to quantum computation and precision measurements are discussed. [Preview Abstract] |
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Y1.00096: Ramsey Spectroscopy on Ultra-Cold ~Alkaline-Earth Atoms Chester Rubbo, Alexey Gorshkov, Ana Rey We consider ultra-cold fermionic alkaline-earth atoms trapped in a deep 3D optical lattice. In these systems, the many-body dynamics driven by the interplay between nuclear spins and two orbital electronic degrees of freedom ($^{1}$S$_{0}$ and $^{3}$P$_{0})$ can be modeled by an effective two-band Hubbard model [Gorshkov, et al. quant-ph/0812.3660]. We analyze the role of interactions, entanglement generation, and inhomogeneities (differential g-factors, vector/tensor light shifts, g etc.) on the sensitivity of precision spectroscopy with these atoms. [Preview Abstract] |
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Y1.00097: Bosonic Atom-Molecule Conversion in an Optical Lattice using Quantum Monte Carlo Jerome Sanders, Juha Javanainen We study the conversion of bosonic atoms to bosonic molecules in an optical lattice via Quantum Monte Carlo (QMC) simulation. The simulation determines the ground state of the many body system in a one-dimensional lattice with periodic boundary conditions. The governing Hamiltonian allows for the tunneling of atoms, the association of atoms, and the dissociation of molecules at any lattice site. This method allows us to study the averages of several runs as well as results from individual runs that may prove to be interesting, but disappear when averaged. We describe the verification and preliminary results of the method on small atom-molecule clusters. [Preview Abstract] |
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Y1.00098: Quantum Phases of Cesium Bose-Einstein Condensates in a two-dimensional Optical Lattice Xibo Zhang, Chen-lung Hung, Nathan Gemelke, Cheng Chin The precise comparison between experiment and the Bose-Hubbard model in determining the phase boundaries of the superfluid to Mott-insulator transitions with ultracold atoms in an optical lattices serves as a first step towards a quantum simulator for many-body physics. Here we report experimental progress on probing phase boundaries using $^{133}$Cs atoms in a thin layer of a two-dimensional optical lattice. A 2D geometry is chosen to remove the inhomogeneity along the imaging direction for a direct determination of the density profile. To load atoms into the 2D optical lattice, we prepare a high aspect ratio BEC of $10^4$ $^{133}$Cs atoms in a trap with weak horizontal and strong vertical confinement provided by a crossed 1064~nm dipole trap and a 10~$\mu$m light sheet, respectively. The BEC is then transferred into a single layer of 4~$\mu$m period vertical lattice, and a two-dimensional horizontal 2D lattice is formed by retroreflecting the crossed dipole trap beams. The on-site interaction is tuned by magnetic Feshbach resonance, and high resolution \emph{in-situ} imaging is performed to probe the phase boundaries at given scattering length and lattice depth. [Preview Abstract] |
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Y1.00099: The Dynamics of Squeezed Coherent States in the Superfuid-Mott Insulator Phase Transition Hyunoo Shim, Thomas Bergeman We propose a theoretical model of number-phase squeezed coherent states in the superfluid to Mott insulator transition, which is capable of representing both quantum phases. We consider for an initial state the superfluid coherent state in a one dimensional Bose-Einstein condensate in a weak optical lattice confined by a harmonic trap. The system enters the Mott insulator phase and returns back to the superfluid phase as the optical lattice barrier height increases and decreases respectively. The evolution of the initial state is calculated via the time dependent variational principle with the Bose-Hubbard Hamiltonian including time dependent terms: optical lattice height, nonlinear on-site interaction, and site-to-site hopping terms. Accordingly the initial state transforms to a squeezed coherent state, a generalization of the coherent state that preserves the minimum uncertainty. We will demonstrate that the dynamics of the above squeezed coherent states is well-suited to understanding the superfluid to Mott insulator quantum phase transition at zero temperature. We will show numerical calculations of a superfluid order parameter, one body density matrix, number-phase variance, and coherence factor revealing that the system is effectively in transion from a superfluid to a Mott insulator. [Preview Abstract] |
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Y1.00100: Toward a nanoscience emulator with two dimensional atomic gases Ping Wang, Q. Ma, S. Dutta, Yong P. Chen We report our experimental progress in constructing a cold atom apparatus for emulating phenomena in nanoscience using low dimensional atom gases. Our first experiments will be performed with a 2D $^{87}$Rb Bose-Einstein condensate created in an optical lattice. Our compact vacuum system consists of two AR-coated glass cells --- a low vacuum magneto-optical trap (MOT) chamber and a high vacuum ``science chamber'', connected by a 15cm-long tube for differential pumping. We have used elliptically shaped cooling laser beams and magnet field coils to realize an elongated MOT in the first chamber, and transferred the atoms to a second MOT in the science chamber by a push laser beam. In the science chamber, a 50W, 1550nm single frequency erbium fiber laser is used to produce an optical dipole trap and optical lattice.In addition, controllable disorder can be introduced with laser speckle and inter-atomic interactions can be tuned by atomic density or Feshbach resonance. We plan to explore important phenomena in nanoscience, such as 2D disorder-induced conductor-insulator transition, quantum Hall effect and graphene-like physics in such a tunable 2D atomic gas in optical lattices. [Preview Abstract] |
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Y1.00101: ABSTRACT WITHDRAWN |
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Y1.00102: Investigation of the 3D to 1D Crossover of a Spin- Imbalanced Fermi Gas Tobias Paprotta, Yean-An Liao, Wenhui Li, Ann Sophie C. Rittner, Randall G. Hulet Spin-imbalanced Fermi gases have been investigated in 3D geometries, for which phase separation into normal and superfluid phases has been observed\footnote{G. B. Partridge et al., Science 311, 503-505 (2006); C.H. Schunck et al., Science 316, 867-870 (2007).}. We have implemented a 2D optical lattice, which produces an array of 1D tubes with weak axial confinement and have begun to map out the phase diagram for the imbalanced Fermi gas in 1D. Theory predicts an inverted spatial position of the unpolarized superfluid relative to 3D, occupying the trap edges rather than the trap center\footnote{G. Orso, Phys. Rev. Lett. 98, 070402 (2007); H. Hu et. al, Phys. Rev. Lett. 98, 070403 (2007).}. We investigate this crossover by tuning lattice depth, which smoothly modifies the inter-tube tunneling. [Preview Abstract] |
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Y1.00103: ULTRACOLD COLLISIONS AND PHOTOASSOCIATION PROCESSES |
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Y1.00104: Exact computation of the scattering length I. Simbotin, Z. Pavlovic, R. C\^ot\'e We present an approach for the exact computation of the scattering length. Our numerical solution takes into account the full tail of the potential energy $V(R)$, and is thus highly accurate. Our approach is based on a change of variable $x=1/R$ at a large enough distance R. The short-range propagation of the solution is done as usual (in $R$), and at $R=R_{\mathrm{mid}}$, we switch to the new variable $x$, which allows to compress the infinite tail into a manageable compact interval for $x:\ [0,1]$. This approach is very convenient and can be implemented with almost any existing propagator. We have tested two numerical methods (log-derivative, and an integral-equation based method) against exactly/analytically soluble potentials of Lennard--Jones type. The agreement between the computed and analytical results reaches a relative error of $10^{-12}$ or better. [Preview Abstract] |
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Y1.00105: Collisional dynamics of ultracold Sr in an optical dipole trap Mi Yan, Yenny Martinez de Escobar, Pascal Mickelson, Thomas Killian A model for describing inelastic and elastic collision dynamics of atoms in an optical dipole trap (ODT) is presented, which is capable of describing traps with little or no spatial symmetry and atomic samples with relatively small ratios of trap depth to atom equilibrium temperature. We apply this model to $^{88}$\textit{Sr }in ODT which has well-characterized collisional properties and compare results of model with measurements. [Preview Abstract] |
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Y1.00106: Collision-induced spin depolarization of alkali-metal atoms in cold $^3$He gas T.V. Tscherbul, P. Zhang, H.R. Sadeghpour, A. Dalgarno, N. Brahms, Y.S. Au, J.M. Doyle We report a combined experimental and theoretical study of spin exchange in collisions of the alkali metal atoms with $^3$He in the presence of an external magnetic field. The lifetime of magnetically trapped $^7$Li and $^{39}$K atoms is measured, allowing for the extraction of lower bounds to the ratios of elastic and spin depolarization rates. We use accurate ab initio calculations to evaluate the Fermi contact interaction constants for Li, Na, K, and Rb atoms interacting with $^3$He. The calculated spin exchange rates are in good agreement with the values measured in spin exchange optical pumping experiments. It is concluded that the alkali metal atoms in a buffer gas of $^3$He have extremely small spin depolarization rates, suggesting a number of potential applications in precision spectroscopy and quantum optics. Phys. Rev. A {\bf 78}, 060703(R) (2008). [Preview Abstract] |
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Y1.00107: Velocity Changing Collisions and Optical Pumping in Ultracold Neutral Plasmas Jose Castro, Thomas Killian The rate of velocity changing collisions in Strontium Ultracold Neutral Plasmas (UNP) was measured through optical pumping between the two ground level spin states. The spin states of the ground and excited levels of a Sr ion form a $\Lambda$ energy configuration when coupled with the appropriate circularly-polarized light. The evolution of the population of such energy states is strongly affected by collisions between ions. Fluorescence measurements of optical pumping into the``dark'' ground level spin state show that velocity changing collisions between ions slow down the pumping rate. A set of coupled rate equations is used in combination with the fluorescence measurements to model the energy level population and to calculate the ion- collisional frequency. [Preview Abstract] |
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Y1.00108: The emergence of an universal picture: the four-body legacy of the Efimov effect Jose P. D'Incao, Javier von Stecher, Chris H. Greene We study universality in the four-boson problem and determine its relation to the three-body Efimov physics. While we confirm the conclusion reached previously by some studies that no true Efimov effect exists for four particles, we demonstrate the existence of an universal class of four-body states that are intimately connected with Efimov states. We have found precisely two four-boson states associated to each Efimov trimer and whose ratio between their energies is a universal number, i.e., irrespective to the details of the interparticle interactions. Both energy spectrum and scattering observables manifest this fundamental connection between three- and four-body physics through the existence of a geometric scaling originated entirely from the Efimov physics. Our study open up way in which such four-body universal physics can be observed in ultracold gases through the analysis of four-body scattering observables. This work was supported by the National Science Foundation. [Preview Abstract] |
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Y1.00109: Quantum calculations of H$_2$--H$_2$ collisions: from ultracold to thermal energies Goulven Qu\'em\'ener, Roman Krems, Balakrishnan Naduvalath We present quantum dynamics of rotational and vibrational energy transfer in collisions between two para-H$_2$ molecules over a wide range of energies spanning the ultracold limit to thermal energies. The calculations were carried out using a quantum scattering code [1] that solves the time-independent Schr\"odinger equation in its full-dimensionality without any angular momentum decoupling approximations. The sensitivity of the results to details of the interaction potential as well as the initial vibrational and rotational quantum numbers of the H$_2$ molecules is explored. Cross sections and rate coefficients for elastic and inelastic collisions from our calculations are compared with available experimental and theoretical results [2,3].\\ References: [1] R. V. Krems, TwoBC - quantum scattering program, University of British Columbia, Vancouver, Canada (2006); [2] G. Qu\'em\'ener, N. Balakrishnan, and R. V. Krems, Phys. Rev. A {\bf 77}, 030704(R) (2008); [3] G. Qu\'em\'ener and N. Balakrishnan, arXiv:0812.3866 (accepted in J. Chem. Phys.). [Preview Abstract] |
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Y1.00110: Quantum dynamics of the O+OH reaction: from ultracold collisions to astrochemistry Balakrishnan Naduvalath, Goulven Qu\'em\'ener, Brian Kendrick We present quantum dynamics of the O+OH$ \to$ H+O$_2$ reaction at temperatures ranging from the ultracold limit to astrophysically relevant values. Two different potential energy surfaces for the HO$_2$ system are employed in the calculations and the sensitivity of the rate coefficients to the details of the interaction potential is explored. The zero-temperature limiting value of the rate coefficient is predicted to be about $6 \times 10^{-12}$ cm$^3$ s$^{-1}$ [1], a value comparable to that of barrierless alkali metal atom - dimer systems. It is found that the rate coefficient remains largely constant in the astrophysically relevant temperature range 10 -- 39~K [2], in agreement with the conclusions of a recent experimental study [3]. Implications of our findings to oxygen chemistry in the interstellar medium are discussed.\\ References: [1] Qu\'em\'ener et al., arXiv:0811.4377v1 (accepted in Phys. Rev. A); [2] G. Qu\'em\'ener, N. Balakrishnan, and B. K. Kendrick, J. Chem. Phys. {\bf 129}, 224309 (2008); [3] Carty et al., J. Phys. Chem. A {\bf 110}, 3101 (2006). [Preview Abstract] |
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Y1.00111: Computational Studies of Many-Body Interactions in Ultra-cold Rydberg Atoms in a Crossed Beam Geometry Thomas Carroll, Christopher Daniel, Michael Noel Ultra-cold highly-excited atoms in a magneto-optical trap are strongly coupled by the dipole-dipole interaction. We have developed a computational model of these systems in order to explore the importance of many-body effects, time dependence, and the geometry of the sample. The model simulates the time evolution of groups of Rydberg atoms in different geometric arrangements. Parallel computing techniques are used to simulate large numbers of atoms directly. Simulation results are presented for two perpendicular, roughly cylindrical, intersecting volumes. The atoms in each cylinder are able to interact with the atoms in the other cylinder, but not within their own cylinder. Results are interpreted in the context of potential experimental parameters. [Preview Abstract] |
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Y1.00112: Enhanced scattering amplitude at short internuclear distances in the photoassociation of ultracold LiCs molecules P. Pellegrini, R. C\^ot\'e, O. Dulieu, J. Deiglmayr, A. Grochola, M. Repp, R. Wester, M. Weidem\"uller The realization of a dense and stable sample of heteronuclear diatomic molecules is the subject of an important research effort. The permanent dipole moments that can be found in these systems offer many new applications and phenomena. Photoassociation (PA) of ultracold atoms is widely used to form ultracold molecules. Although it usually leads to the formation of highly excited vibrational molecules, it was recently used to achieve a gas of ultracold LiCs molecules in their absolute ground level [Deiglmayr et al., Phys. Rev. Lett. 101, 133004 (2008)]. Here we present the theoretical analysis of the above-mentioned PA experiment. A full quantum coupled-channel calculation was performed for the determination of the initial scattering wave-function and absolute PA rates at large detuning were calculated. The high measured PA rates were found to be the consequence of a broad Feshbach resonance which strongly perturbed the initial collisional wave function at short internuclear distances. This effect can appear in other systems and opens interesting perspectives for the formation of ultracold molecular gases. [Preview Abstract] |
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Y1.00113: Threshold laws for N-body recombination Nirav Mehta, Seth Rittenhouse, Jose D'Incao, Javier Von Stecher, Chris Greene We present a formula for the cross section and event rate constant describing recombination of N particles in terms of general S-matrix elements. Our result immediately yields the generalized Wigner threshold scaling (with respect to energy and scattering length) for the recombination of N bosons. Specifically we find that the four-boson recombination rate approaches a constant at the collision threshold energy, and hence four-body recombination can potentially be competitive with three-body recombination in contributing to atomic losses. Further, we explore the resonant modification of recombination by the presence of universal four-boson states near threshold. [Preview Abstract] |
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Y1.00114: Vibrational quantum defect for the analysis of weakly bound molecules. Application to Rubidium and cesium data. L. Pruvost, H. Jelassi, B. Viaris de Lesegno In the context of cold molecules physics, the spectroscopic data and their analysis play a very important role. The photoassociation spectroscopy of alkali dimmers, performed by laser excitation of cold atoms, is one of the methods providing high-resolution data about the vibrational levels lying close to the dissociation limit. Such weakly bound molecules are described by the dipole-dipole interaction, i.e. -1/R$^3$ where R is the inter-nuclear distance and their eigen energies are close to the Le Roy-Bernstein formula [1]. The discrepancies to the formula law are due to the short-range interactions of the potential and to couplings between potentials. We have expressed the discrepancies via a parameter, the vibrational quantum defect (VQD), defined similar to the atomic quantum defect [2]. The VQD deduced from the data and plotted versus the energy allows us to emphasize the couplings. Furthermore, a fit of the graph using a 2-channel model provides the value of the coupling and a characterization of the 2 potentials. We have applied the method 5s$_{1/2}$-5p$_{1/2}$0u+ data of Rb2 recorded in our group [3] and 6s$_{1/2}$-6p$_{1/2}$0u+ data of Cs2 recorded in Stwalley group [4]. The coupling due to spin-orbit interaction has been deduced, the perturbing levels identified and the wavefunction mixing deduced. [1] R. J. Le Roy , R. B. Bernstein, J. Chem. Phys. \textbf{52}, 3869, 1970. [2] H. Jelassi et al., Phys. Rev. A. \textbf{73}, 32501, 2006. [3] H. Jelassi et al., Phys. Rev. A. \textbf{74}, 12510, 2006. [4] H. Jelassi, et al., Phys. Rev. A \textbf{78}, 022503, 2008. [Preview Abstract] |
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Y1.00115: APPLICATIONS OF AMO SCIENCE |
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Y1.00116: Nuclear Wavepacket Propogation Model for the Retinal Chromophore in Rhodopsin Brittany Corn, Svetlana Malinovskaya Rhodopsin, consisting of a retinal chromophore and a protein opsin, is responsible for the first steps in the vision process through a cis to trans photoisomerization, which is completed within 200 fs[1]. Efforts to control the ultrafast dynamics of this molecule have been carried out experimentally[2] as well as through quantum mechanical modeling of nuclear wave packet propagation[3]. We propose a two state model in which the ground electronic Potential Energy Surface (PES) is made up of two adjacent harmonic potentials, representing the cis and trans retinal saddle points, as well as an excited PES, characterized by the Morse potential, which meets the ground PES at a conical intersection. We explore the achievement of a high quantum yield of the trans retinal configuration by varying parameters of the external field and choosing the most adequate shape. Another investigation is presented in which we compare the charge distribution of cis and trans retinal in order to reveal a charge transfer mechanism behind the isomerization of rhodopsin. The results of the Lowdin and Natural Population Analyses demonstrate a significant transfer of charge in and around the isomerization region. [1] RW Schoenlein, LA Peteanu, RA Mathies, CV Shank, Science 254, 412 (1991) [2] VI Prokhorenko, AM Nagy, SA Waschuk, LS Brown, RR Birge, RJD Miller, Science 313, 1257 (2006) [3] S Hahn, G Stock, Chem Phys 259, 297-312 (2000) [Preview Abstract] |
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Y1.00117: Selective two-photon excitation of fluorescent biomarkers by coherent control and pulse shaping Milan Poudel, Alexandre Kolomenskii, Alvin T. Yeh, Hans Schuessler Two-photon fluorescence of organic dyes and biomarkers was successfully optimized by using a feedback control femtosecond pulse shaping technique. For optimization we implemented a liquid crystal pulse shaper in a folded 4f set-up with an evolutionary algorithm. The optimization procedure that started with a near transform-limited pulse noticeably improved the two-photon fluorescence. Several signal ratios involving two-photon fluorescence, second harmonic generation and the incident laser power were successfully optimized. Theoretical calculations were done and optimal parameters were found for the best results. Experiment on selective excitation of individual dyes within a mixture of common biomarkers namely Texas Red, Indo-1 and FITC are under way. For this research amplified spectrally broad 7 femtosecond pulses appropriately shaped with an acoustic optical programmable filter (Dazzler) are used. Such a selective excitation of specific biomarkers is of great importance for two-photon microscopy and understanding the roles of different biomolecules in vital processes. [Preview Abstract] |
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Y1.00118: Probing sub-alveolar length scales with hyperpolarized-gas diffusion NMR Wilson Miller, Michael Carl, Karen Mooney, John Mugler, Gordon Cates Diffusion MRI of the lung is a promising technique for detecting alterations of normal lung microstructure in diseases such as emphysema. The length scale being probed using this technique is related to the time scale over which the helium-3 or xenon-129 diffusion is observed. We have developed new MR pulse sequence methods for making diffusivity measurements at sub-millisecond diffusion times, allowing one to probe smaller length scales than previously possible in-vivo, and opening the possibility of making quantitative measurements of the ratio of surface area to volume (S/V) in the lung airspaces. The quantitative accuracy of simulated and experimental measurements in microstructure phantoms will be discussed, and preliminary in-vivo results will be presented. [Preview Abstract] |
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Y1.00119: Dose Volume Histogram (DVH) Analysis in Intensity Modulation Radiation Therapy (IMRT) Treatments for Prostate Cancers Anil Pyakuryal Studies have shown that as many as 8 out of 10 men had prostate cancer by age 80.Prostate cancer begins with small changes (prostatic intraepithelial neoplasia(PIN)) in size and shape of prostate gland cells,known as prostate adenocarcinoma.With advent in technology, prostate cancer has been the most widely used application of IMRT with the longest follow-up periods.Prostate cancer fits the ideal target criteria for IMRT of adjacent sensitive dose-limiting tissue (rectal, bladder).A retrospective study was performed on 10 prostate cancer patients treated with radiation to a limited pelvic field with a standard 4 field arrangements at dose 45 Gy, and an IMRT boost field to a total isocenter dose of 75 Gy.Plans were simulated for 4 field and the supplementary IMRT treatments with proposed dose delivery at 1.5 Gy/fraction in BID basis.An automated DVH analysis software, \textbf{\textit{HART }}\textbf{(}S. Jang et al., 2008,Med Phys \textbf{35},p.2812)was used to perform DVH assessments in IMRT plans.A statistical analysis of dose coverage at targets in prostate gland and neighboring critical organs,and the plan indices(homogeneity, conformality etc) evaluations were also performed using HART extracted DVH statistics.Analyzed results showed a better correlation with the proposed outcomes (TCP, NTCP) of the treatments. [Preview Abstract] |
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Y1.00120: SEOP polarization of 3He and 129Xe at high volumetric rates I. Ruset, D. Watt, J. Distelbrink, J. Brackett, J. Ketel, S. Ketel, W. Porter, T. Upton, W. Hersman New regimes for production of polarized 3He and 129Xe using Spin Exchange Optical Pumping are under study for the purpose of increasing volumetric production rates, output polarization, or both. For polarized 129Xe production, photon efficiency is increased by polarizing at low xenon partial pressure. Higher spin exchange rates between alkali atoms and the xenon nucleus are accessed by exploiting longer lived van der Waals molecules at lower buffer gas pressures. High production rates are accomplished by flowing at high volumetric rates and illuminating with a high power, narrowed line laser. Polarizations of 129Xe exceeding 70{\%} at production rates of 3 SLPH were observed. For polarized 3He production, efficiency is maximized by selecting a high operating temperature and an alkali mixture rich in potassium. High volumetric production rate is accomplished by illuminating a large 8 L high-pressure 3He reservoir with a high power (broad) diode stack. We estimate that 50 L can be polarized through three exponential ramp-up times in 12 hours, yielding as much as 100 L/day. Asymptotic 3He polarization will be reported. [Preview Abstract] |
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Y1.00121: Recent Advances in Laser-Polarized He-3 Targets for Electron Scattering Jaideep Singh, Peter Dolph, Karen Mooney, Vladimir Nelyubin, Al Tobias, Aidan Kelleher, Todd Averett, Gordon Cates Laser-polarized He-3 has long been proven to be extremely useful for exploring the structure of the neutron in electron-scattering experiments. Using spin-exchange optical pumping (SEOP), the He-3 polarization of these high-density (10 amagats) two-chamber target cells now regularly approaches 70\%. This remarkable performance has been achieved by taking advantage of both alkali-hybrid SEOP and high-power spectrally-narrowed diode lasers. In this talk, we'll share what we've learned about (1) applying these new technologies and (2) the factors that are limiting the He-3 polarization in these target cells. [Preview Abstract] |
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Y1.00122: Laser frequency combs for precision astrophysical spectroscopy Chih-Hao Li, David F. Phillips, Andrew Benedick, Alex Glenday, Franz X. Kaertner, Dimitar Sasselov, Andrew Szentgyorgi, Ronald L. Walsworth, Claire Cramer Spectroscopy is a crucial tool for cosmology and the search for extrasolar planets. Broadband frequency combs have revolutionized precision spectroscopy in the laboratory with absolute frequencies determined to better than one part in $10^{15}$. Good long-term stability and reproducibility are also major advantages of the frequency comb. However, their application to any astrophysical spectrograph requires increasing the comb-line spacing by at least 10-fold from today's high repetition rate sources operating at about 1 GHz. We report the successful operation of a 40-GHz comb generated from a 1-GHz source, without compromise on long-term stability, reproducibility and resolution at an astronomical observatory. The application of this novel technique to astrophysics should allow more than a 10-fold improvement in Doppler-shift sensitivity, with significant impact to many fields, including the search for extrasolar Earths, the direct measurement of the universe expansion and the detection of the temporal variation of physical constants. [Preview Abstract] |
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Y1.00123: Femtosecond laser frequency comb for precision astrophysical spectroscopy Alex Glenday, Claire Cramer, Andrew Benedick, Chih-Hao Li, Franz X. Kaertner, David F. Phillips, Andrew Szentgyorgi, Ronald L. Walsworth Spectroscopy is a crucial tool for cosmology and the search for extrasolar planets. Broadband frequency combs have revolutionized precision spectroscopy in the laboratory with absolute frequencies determined to better than one part in $10^{15}$. Good long-term stability and reproducibility are also major advantages of the frequency comb. However, their application to any astrophysical spectrograph requires increasing the comb-line spacing by at least 10-fold from today's high repetition rate sources operating at about 1 GHz. We report measurements of a 39-GHz comb generated from a 1-GHz source using the TRES spectrograph at the Fred Lawrence Whipple Observatory. Repeated measurements show that we can reach the expected stability limit of the spectrograph. The application of this novel technique to astrophysics should allow more than a 10-fold improvement in Doppler-shift sensitivity, with significant impact to many fields, including the search for extrasolar Earths, the direct measurement of the universe expansion and the detection of the temporal variation of physical constants. [Preview Abstract] |
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Y1.00124: A coupled optoelectronic oscillator by using an actively mode-locked external-cavity diode laser Tai Hyun Yoon, Jeongmin Lee, Gwang Hoon Jang, Duseong Yoon, Minsoo Song We propose and demonstrate a novel coupled optoelectronic oscillator consisting of an actively mode-locked external- cavity diode laser (ECDL) at 852 nm and a microwave feed-back loop. We show that the oscillation frequency can be precisely tuned by varying the feedback phase and the frequency tuning slope depends only on the reflectivity of the output coupler of the ECDL. In the proof-of-principle experiment, we found that the phase noise spectrum and frequency stability of the microwave carrier frequency at 2.298 GHz was dominated by the quality factor of the ECDL cavity, i.e., the Leeson frequency of the optical resonator. This feature could be understood since the Leeson frequency is inversely proportional to the $Q$- value of the feed-back resonator. Our COEO has a great potential as a compact and portable optoelectronic oscillator that generates a highly-stable microwave reference frequency, for instance, by stabilizing the repetition frequency to the hyperfine transition of Cs atoms at 9.2 GHz. [Preview Abstract] |
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Y1.00125: Cold Fusion Dark Matter and Dark Energy Mark Levi Explanation of Cold Fusion [1] ``It is k-capture forming dineutrons followed by absorption by palladium.'' with excess heat energy no more than about .15 MeV per nucleon. Experimentally [1], $^1$H and electrons are at high pressure at the center of a palladium wire sample, ``After hours of loading with $^1$H, bubbles were present on the wire surface and the wire's resistance had stopped increasing, there was a fizz of hydrogen from the wire within a few seconds after loading current and large bubbles were stopped.'' a repeatable cycle. K-capture rate is affected by environment at the 1/10000 level has has been known since 1946 ( ref. [6]in [1]); and recently has been seen at the 0.35\% level for 7Be in C60 [2]. Neutron halos have been seen recently in 8He [3], 6He [4] and others long ago. Conclusions: 1) the evidence for dineutrons is fairly good and as in all K-captures is accompanied by a neutrino emission. collapse of a star to a neutron star has a succession of K-captures in conditions like cold fusion i.e. high pressure. 2)Dark matter is dineutrons from formation of neutron stars and black holes, and dark energy of neutrinos generated in neutron stars, ordinary stars and black holes. If in the latter, then their mass must be zero for an infinite horizon. References: [1] M. Levi, DAMOP Meeting poster paper, session WP, 16-19 May,1995 [2]T. Ohtsuku et al., Phys. Rev. Lett. 98, 252501 (2007) [3] V. I. Ryjkov et al., Phys. Rev. Lett. 101, 01901 (2008) [4] L. B. Wang et al., Phys. Rev. Lett. 93 ,142501 (2004). [Preview Abstract] |
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