Bulletin of the American Physical Society
39th Annual Meeting of the APS Division of Atomic, Molecular, and Optical Physics
Volume 53, Number 7
Tuesday–Saturday, May 27–31, 2008; State College, Pennsylvania
Session P3: Focus Session: Atomic Polarization and Dispersion |
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Chair: Hossein Sadeghpour, ITAMP, Harvard University Room: Keller Building 104 |
Friday, May 30, 2008 11:00AM - 11:36AM |
P3.00001: Calculation of the dispersion interaction between two atoms Invited Speaker: General procedures for systematically evaluating the long range interaction between two atoms in arbitrary states have been developed for the separate cases of two homo-nuclear atoms and two hetero-nuclear atoms. Practical calculations for the dispersion coefficients, $C_6$, $C_8$ and $C_{10}$ are made by evaluating intermediate state sum rules of reduced matrix elements. Cases with a number of asymptotic states energetically close together are best described by recourse to the Feshbach formalism. Sets of reduced matrix elements to describe the excitation spectra of H, He, the rare gases, the alkali atoms and the alkaline- earth atoms have been gradually accumulated. Consequently, it is possible to evaluate the dispersion interaction for many combinations of the low lying states involving these atoms. The accuracy of these parameters ultimately depends on the accuracy of the representation of the excited atoms. The frozen core model used is capable of giving good agreement with relativistic many-body calculations for selected atom pairs provided the core is properly included in all aspects of dispersion calculation. [Preview Abstract] |
Friday, May 30, 2008 11:36AM - 11:48AM |
P3.00002: Polarizability of Mg$^{+}$ from fine structure measurements of high-L Rydberg states of magnesium. Erica L. Snow, Stephen R. Lundeen Microwave spectroscopy studies by means of selective laser excitation with detection of Rydberg levels by Stark ionization have been used to measure the fine structure intervals of n=17 for a range of angular momentum states, $6\le L\le 11$, in magnesium. The long-range polarization model was used to extract the dipole and quadrupole polarizability of Mg$^{+}$ from the fine structure data. Contributions due to higher order terms in the polarization model, which are known to affect the interpretation of the quadrupole polarizability in similar cases, such as barium and Si$^{2+}$, were evaluated. The experimental data and the results of the analysis will be presented. [Preview Abstract] |
Friday, May 30, 2008 11:48AM - 12:00PM |
P3.00003: Relativistic many-body calculation of energies, lifetimes, hyperfine constants, and polarizabilities in $^{7}$Li W.R. Johnson, U.I. Safronova, A. Derevianko, M.S. Safronova Excitation energies of $ns$, $np$, $nd$, and $nf$ ($n \leq$ 6) states in neutral lithium are evaluated within the framework of relativistic many-body theory. First-, second-, third-, and all-order Coulomb energies and first- and second-order Breit corrections to energies are calculated. All-order calculations of reduced matrix elements, oscillator strengths, transition rates, and lifetimes are given for levels up to $n$ = 4. Electric- dipole ($2s\ -np$), electric-quadrupole ($2s\ -nd$), and electric-octupole ($2s\ -nf$), matrix elements are evaluated to obtain the corresponding ground state multipole polarizabilities using the sum-over-states approach. Scalar and tensor polarizabilities for the $2p_{1/2}$ and $2p_{3/2}$ states are also calculated. Magnetic dipole hyperfine constants $A$ are determined for low-lying levels up to $n$ = 4. The quadratic Stark shift for the $(F = 2\ M =0) \leftrightarrow (F = 1\ M =0)$ ground-state hyperfine transition is found to be -0.0582 Hz/(kV/cm)$^2$, in slight disagreement with the experimental value -0.061$\pm$0.002 Hz/(kV/cm)$^2$. Matrix elements used in evaluating polarizabilities, hyperfine constants, and the quadratic Stark shift are obtained using all-order method. [Preview Abstract] |
Friday, May 30, 2008 12:00PM - 12:12PM |
P3.00004: Single ion measurement of the branching ratios of the 6P$_{3/2}$ decay in BaII N. Kurz, M.R. Dietrich, G. Shu, J.S. Salacka, R. Bowler, B.B. Blinov We report a new measurement of the branching ratios of the 6P$_{3/2}$ state decay of $^{138}$Ba$^{+}$ into the 5D$_{5/2}$ and 5D$_{3/2}$ states. The measurement was performed on a single ion in a linear Paul trap excited with 455 nm light from a doubled mode-locked Ti:Sapphire laser driving the 6S$_{1/2}$ -- 6P$_{3/2}$ transition, followed by detecting the ion's fluorescence on the 6S$_{1/2}$ - 6P$_{1/2}$ cooling transition. The use of a single ion in ultrahigh vacuum eliminates many of the systematics of the earlier measurements. Excluding decays directly to the ground state, we determine ratios of 0.881 and 0.118 for the 5D$_{5/2}$ and 5D$_{3/2}$ decays respectively with a 3{\%} statistical and 1{\%} systematic error. This is an improvement of a factor of three over previously reported data [1]. This level of precision is sufficient to compare to numerical calculations [2]. Work is underway to establish absolute values for all three ratios (6P$_{3/2}\to $6S$_{1/2}$, 5D$_{3/2}$, 5D$_{5/2})$ by driving a $\pi $ Rabi rotation on the 6S$_{1/2}$ -- 6P$_{3/2}$ transition with a single laser pulse. $^{1}$ Kastberg, et.al., \textit{J Opt. Soc. Am. B} \textbf{10}, 1330-6, (1993). $^{2}$ Gopakumar, G., \textit{Phys. Rev. A} \textbf{66 }032505-1-6, (2002). [Preview Abstract] |
Friday, May 30, 2008 12:12PM - 12:48PM |
P3.00005: Polarizabilities, Atomic Clocks, and Magic Wavelengths Invited Speaker: I will describe the high-precision calculations of the static and frequency-dependent polarizabilities in alkali-metal atoms and Ca$^+$. The resulting polarizability values are used for a variety of applications from reducing the decoherence in quantum logic gates to the evaluation of the black-body radiation (BBR) shifts for optical frequency standards. Our alkali-metal atom polarizability calculations can be used to predict the oscillation frequencies of optically-trapped atoms, and particularly the ratios of frequencies of different species held in the same trap. We identify wavelengths at which two different alkali atoms have the same oscillation frequency. We also evaluate ``magic'' wavelengths in alkali-metal atoms for which $np$ and $ns$ levels have the same ac-Stark shift enabling state-insensitive optical cooling and trapping. The calculation of the BBR shift for the optical frequency standard with Ca$^+$ ion is also described. [Preview Abstract] |
Friday, May 30, 2008 12:48PM - 1:00PM |
P3.00006: Precision Measurement of the Rb D2 Transition Linewidth at Ultralow Temperature Brad Schultz, George Noble, He Ming, William van Wijngaarden The Rb D2 linewidth was studied using atoms cooled to a temperature of 50 $\mu $K that were contained in a magneto-optical trap. The transmission of a probe laser through the atom cloud was monitored using a CCD detector. The probe laser frequency was scanned across the resonance using an acousto-optic modulator. The observed lineshape was very well fitted by a Lorentzian function. The full width half maximum linewidth was examined as a function of the optical depth and the probe laser intensity. The extrapolated value at zero optical depth was determined with an accuracy of 0.3{\%}. This corresponds to a radiative lifetime of the 5P$_{3/2}$ state that is consistent with results determined by measuring the temporal decay of fluorescence or photoassociation spectroscopy. The experimental results are slightly less than that computed using relativistic many body perturbation theory. [Preview Abstract] |
Friday, May 30, 2008 1:00PM - 1:12PM |
P3.00007: Lifetime measurements of the rubidium 5D states Dong Sheng, Adrian Perez Galvan, Luis Orozco We present lifetime measurements of the 5D3/2 and 5D5/2 excited states of rubidium using correlated single photon detection. We perform the experiment in a small sample of magneto-optically trapped Rb87 atoms and prepare the 5D states using a two-photon excitation with the 5P3/2 state as the intermediate state. We directly measure the 762 nm photon from the decay of the 5D3/2 state to the 5P1/2 state to obtain the lifetime of the 5D3/2 state. We detect the 420nm photon from the cascade decay of the 5D5/2 state to the 5S1/2 state through the 6P3/2 state to extract the lifetime of the 5D5/2 state. We have reached statistical errors of less than 2 percent for the lifetimes of those two 5D states and we are in the process of studying systematic errors, including the density of the atomic sample, the intensity of the excitation beams, the magnetic field environment, and the fitting algorithm. [Preview Abstract] |
Friday, May 30, 2008 1:12PM - 1:24PM |
P3.00008: Theoretical study of the K, Rb, and Fr lifetimes Eugeniya Iskrenova Tchoukova, Marianna Safronova We calculate $ns$, $np$, and $nd$ lifetimes in K, Rb, and Fr using relativistic high-precision all-order method where all single and double excitations of the Dirac-Hartree-Fock wave function are included to all orders of perturbation theory. Additional calculations are carried out where necessary to account in part for effects of valence triple excitations and to evaluate the uncertainty of the calculations. The data are compared with available experimental values. Our calculations provide benchmark data for a number of E1 matrix elements and branching ratios. We identify lifetimes that are particular useful for tests of high-precision theory owing to extremely large correlations to certain electric-dipole matrix elements. Fr calculations are motivated also by the study of parity nonconservation with this atom [1]. \\ \noindent [1] G. Gwinner, E. Gomez, L. A. Orozco, A. Perez Galvan, D. Sheng, Y. Zhao, G. D. Sprouse, J. A. Behr, K. P. Jackson, M. R. Pearson, S. Aubin, and V. V. Flambaum, Hyp. Int. 172 , 45 (2006). [Preview Abstract] |
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