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 Q5: Clocks, Precision Measurements, and Atomic/Molecular Structure |
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Chair: Kurt Gibble, Penn State University Room: Nittany Lion Inn Boardroom I |
Friday, May 30, 2008 2:00PM - 2:12PM |
Q5.00001: Systematic evaluation of a strontium optical lattice clock at 1x10$^{-16}$ Gretchen K. Campbell, Andrew D. Ludlow, Sebastian Blatt, Tanya Zelevinsky, Martin M. Boyd, Michael J. Martin, Jan W. Thomsen, Jun Ye, Tara M. Fortier, Jason E. Stalnaker, Scott A. Diddams, Chris W. Oates We have recently completed an evaluation of the uncertainty of a $^{87}$Sr optical lattice clock at the 1x$10^{-16}$ fractional level, surpassing the best current evaluations of Cs primary standards. The evaluation was performed using a remote comparison of optical clocks over km-scale urban distances. This allowed us to evaluate the Sr clock located at JILA, against the Ca optical clock operated $\sim$4km away at NIST via an optical fiber link. We will report on the observation of density-dependent effects in the doubly spin-polarized (fermionic) sample. Using a single spin state, and by varying the excitation fraction, we have found experimental parameters for which the density shift of the clock transition is consistent with zero. [Preview Abstract] |
Friday, May 30, 2008 2:12PM - 2:24PM |
Q5.00002: Ytterbium Optical Lattice Clock Nathan Lemke, Zeb Barber, Nicola Poli, Chris Oates, Leo Hollberg We report on an optical clock based on the $^{1}$S$_{0}-^{3}$P$_{0}$ transition in neutral Yb atoms confined to a Stark shift-free optical lattice. Tight confinement of atoms to the Lamb-Dicke regime is shown to suppress Doppler- and recoil-related shifts, while the Stark shift-canceling technique eliminates the clock's first-order sensitivity to lattice intensity. Clocks based on magnetically-induced spectroscopy of $^{174}$Yb (I=0) and state-resolved spectroscopy of $^{171}$Yb (I=1/2) are demonstrated. Comparisons with other optical and microwave frequency standards via a self-referenced femtosecond frequency comb have enabled initial measurements of the absolute frequency and systematic effects with a fractional uncertainty of 10$^{-15}$, a level that can be reached in 10 seconds of averaging time. [Preview Abstract] |
Friday, May 30, 2008 2:24PM - 2:36PM |
Q5.00003: Determination of the fine structure constant with atomic interferometry and Bloch oscillations. Pierre Clad\'e, Malo Cadoret, Estefania de Mirandes, Saida Guellati-Kh\'elifa, Catherine Schwob, Fran\c{c}ois Nez, Lucile Julien, Fran\c{c}ois Biraben We report a new measurement of the recoil of $^{87}$Rb atoms using atomic interferometry and Bloch oscillations of ultracold atoms in an accelerated lattice. For the first time, we combine the high efficiency of Bloch oscillations with the sensitivity of Ramsey-Bord\'e interferometer. Our measurement with a statistical uncertainty of 3.4~ppb combined with a careful study of systematic effects (3.3~ppb) leads to a value of the fine-structure constant with an uncertainty below 5~ppb. [Preview Abstract] |
Friday, May 30, 2008 2:36PM - 2:48PM |
Q5.00004: Precision Laser Spectroscopy of Exotic Helium Isotopes P. Mueller, I.A. Sulai, K. Bailey, R.J. Holt, R.V.F. Janssens, Z.-T. Lu, T.P. O'Connor, A.C.C. Villari, J.A. Alcantara-Nunez, R. Alves-Conde, M. Dubois, C. Eleon, G. Gaubert, N. Lecesne, M.-G. Saint-Laurent, J.-C. Thomas, G.W.F. Drake, L.-B. Wang We have succeeded in laser trapping and cooling of the exotic helium isotopes $^6$He (t$_{1/2}$ = 0.8 sec) and $^8$He (t$_{1/ 2}$ = 0.1 sec), and have performed precision laser spectroscopy on individual trapped atoms. Based on the atomic isotope shifts measured along the isotope chain $^3$He - $^4$He - $^6$He - $^8$He, and on the precise theory of the atomic structure of helium, the nuclear charge radii of $^6$He and $^8$He are determined for the first time independent of nuclear models. The results are compared with the values predicted by nuclear structure calculations of light nuclei and test their ability to characterize these neutron rich, loosely bound halo nuclei. The $^6$He measurement was performed at ATLAS of Argonne, and the $^8$He measurement at GANIL, France. This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357. [Preview Abstract] |
Friday, May 30, 2008 2:48PM - 3:00PM |
Q5.00005: Extending Precision Atomic Mass Measurement to Higher Mass Matthew Redshaw, Brianna Mount, Edmund Myers Precise atomic masses of the alkalis and certain other metals are important for photon-recoil ($h/m)$ determinations of the fine structure constant, while a series of precisely measured atomic masses up to high mass-number would provide convenient references for mass spectrometers used in nuclear physics. Using single ions in a Penning trap, with image charge detection and a phase-coherent technique for measuring the cyclotron frequency, we have measured the atomic masses of various heavy stable atoms, including $^{84,86}$Kr, $^{129,132,136}$Xe, with fractional precision of $\sim $0.1ppb; work on potassium and other alkalis is in progress. The measurements involve comparisons of multi-charged ions with singly-charged ions at similar $m/q$. Systematic errors originating from this difference in charge and other problems relating to high mass will be discussed. [Preview Abstract] |
Friday, May 30, 2008 3:00PM - 3:12PM |
Q5.00006: Improved Measurement of the 1s2s $^{1}$S$_{0}$ -- 1s2p $^{3}$P$_{1}$ Interval in Helium-like Silicon Edmund Myers, Thomas DeVore, David Crosby Using co-linear fast-beam laser spectroscopy with co- and counter-propagating beams we have measured the 1s2s $^{1}$S$_{0}$ -- 1s2p $^{3}$P$_{1}$ intercombination interval in Si$^{12+}$ with the result 7230.585(6) cm$^{-1}$. The experiment made use of a dual-wavelength, high-finesse, power build-up cavity excited by single-frequency lasers at 1319 nm and 1450 nm. The result is a factor of 30 more precise than previous work and will provide a precision test of relativistic atomic theory. [Preview Abstract] |
Friday, May 30, 2008 3:12PM - 3:24PM |
Q5.00007: Hyperfine structure of the metastable $^3P_2$ state of alkaline earth atoms as an accurate probe of nuclear magnetic octupole moments Kyle Beloy, Andrei Derevianko, Walter Johnson Measuring the hyperfine structure (HFS) of long-lived $^3P_2$ states of divalent atoms may offer the opportunity of extracting relatively unexplored nuclear magnetic octupole and electric hexadecapole moments. Here, using relativistic many- body methods of atomic structure and the nuclear shell model, we evaluate the effect of these higher nuclear moments on the hyperfine structure. We find that the sensitivity of HFS interval measurements in $^{87}$Sr needed to reveal the perturbation caused by the nuclear octupole moment is on the order of kHz. Results of similar analyses for $^{9 }$Be, $^{25} $Mg, and $^{43}$Ca are also reported. [Preview Abstract] |
Friday, May 30, 2008 3:24PM - 3:36PM |
Q5.00008: Hyperfine Structure of Trapped $^{137}$Ba$^{+}$ Ions as a Probe of the Nuclear Magnetic Octupole Moment Gary Howell, Boris Blinov, Norval Fortson We present calculations of the 1$^{st}$ order hyperfine splittings in the $^{137}$Ba$^{+}$ ion in terms of the 3 hyperfine constants a, b, and c, and also two 2$^{nd}$-order energy effects, for the metastable states $D_{3/2}$ and $D_{5/2}$. It is shown that up to 2$^{nd}$-order, only one of these 2$^{nd}$ order effects (the dipole-quadrupole term) contributes to the measured value of the magnetic octupole constant c; the dipole-squared term does not contribute. Thus c can be determined purely from the measured energy splittings, with a small correction due to the dipole-quadrupole term. Using the octupole constants c$_{3/2}$ and c$_{5/2}$ of the two sets of levels, a particular linear combination of c$_{3/2}$ and c$_{5/2}$ will be completely independent of the 2$^{nd}$ order dipole-quadrupole correction as well, and expressed purely in terms of the measured energy level splittings. Together with atomic theory calculations of the electronic wavefunctions, this would provide a precise value of the nuclear magnetic octupole moment, which could be used as a test of nuclear models. [Preview Abstract] |
Friday, May 30, 2008 3:36PM - 3:48PM |
Q5.00009: Third-order relativistic many-body calculation of transition probabilities for the beryllium and magnesium isoelectronic sequences Dansha Jiang, Rupsi Pal, Marianna Safronova Third-order relativistic many-body perturbation theory formulas are derived for the calculation of the transition matrix elements in divalent systems. We use one-electron orbitals calculated in the $V^{(N-2)}$ Dirac-Fock (DF) potential of the closed core to start the perturbation expansion. B-splines are used to generate a complete set of DF basis orbitals for the numerical evaluation of the perturbation theory terms. The effect of Breit interation is also investigated. We made a detailed study of all electric-dipole transitions between the low-lying $2l2l'$~ [$LSJ$] states for beryllium-liked ions and $3l3l'$~[$LSJ$] states for magnesium-like ions. Oscillator strength, transition probabilities and lifetimes are evaluated. The size of the third-order correlation correction is investigated. Comparisons are made with other theoretical calculations and experiments. [Preview Abstract] |
Friday, May 30, 2008 3:48PM - 4:00PM |
Q5.00010: Spectroscopy of high pressure cesium discharge Goran Pichler, Marin Pichler Near UV, visible and NIR spectrum of Cs lamp has been studied in many experimental situations. We concentrate on the spectral region around resonance lines where numerous satellite bands appear. We followed the appearance of these satellite bands after the ignition. They first appear in emission, and then in absorption, due to the steady increase of cesium atom density. The origin of the satellite bands have been described \footnote{D. Ve\v za, R. Beuc, S. Milosevi\' c and G. Pichler, Eur. Phys. J. D, \textbf{2}, 45 (1998)}$^{,}$\footnote{R. Beuc, H. Skenderovi\' c, T. Ban, D. Ve\v za, G. Pichler, W. Meyer, Eur. Phys. J.D \textbf{15}, 209 (2001)}. We observed the satellite band intensity behavior in several different burners filled with cesium and xenon. In one burner made out of crystalline sapphire we observed interesting spatial distribution of entire visible spectrum, during evolution in time after the ignition. The intensity behavior of satellite bands in the near-infrared spectral region will be used in further development of the white light source with pulsed cesium high-pressure discharge. [Preview Abstract] |
Friday, May 30, 2008 4:00PM - 4:12PM |
Q5.00011: Collisional-Radiative Modeling of EBIT Spectra from Highly-Charged High-Z Ions Yuri Ralchenko, Ilija N. Draganic, John D. Gillaspy, Joseph N. Tan, Joshua M. Pomeroy, Joseph Reader We present results of collisional-radiative modeling of line spectra from highly-ionized (ion charge z $>$ 35) Hf, Ta, W, and Au in the region 4-20 nm. The spectra were measured with the NIST EBIT and grazing incidence spectrograph. Good experimental resolution along with the non-Maxwellian nature of the low-density EBIT plasma require both a detailed account of ion level structure and a large amount of collisional data. The atomic data generated with the Flexible Atomic Code [1] were used in simulations with the non-Maxwellian code NOMAD [2]. Good quantitative agreement between the simulated spectra and the observations allowed reliable identification of tens of new spectral lines which can be used for diagnostic purposes for fusion reactors. [1]. M.F.Gu, Astroph. J. 582, 1241 (2003). [2]. Yu.V. Ralchenko and Y. Maron, JQSRT 71, 609 (2001). [Preview Abstract] |
Friday, May 30, 2008 4:12PM - 4:24PM |
Q5.00012: The Ion $H_3^{+}$ in a Strong Magnetic Field Nicolais Guevara Leon, Alexander V. Turbiner, Juan C. Lopez Vieyra A detailed study of the low-lying electronic states of the $H_3^+$ molecular ion in linear parallel configuration is carried out for $B=0-\mbox {4.414}\times 10^{13}$\,G in the Born-Oppenheimer approximation. It is shown that the ground state depends on the magnetic field strength. It evolves from the spin-singlet $^1 \Sigma_g$ for small magnetic fields $B\leq 5\times 10^{8}$\,G to the weakly-bound spin- triplet $^3\Sigma_u$ for intermediate fields and eventually to the strongly-bound spin-triplet $^3\Pi_u$ state for $5 \times 10^{10}\,$G$\leq B \leq 4.414 \times 10^{13}\,$G. For $B \geq 5 \times 10^{10}\,$G the $H_3^+$ molecular ion is stable towards all possible ionization and dissociation channels. [Preview Abstract] |
Friday, May 30, 2008 4:24PM - 4:36PM |
Q5.00013: Searching for allotropes of Wigner crystal clusters with Genetic Algorithm Matt Kalinski We have recently discovered the configuration existence theorem for N electrons in magnetic and circularly polarized fields stating that the maximum number of configurations may be the product of all differential foldings [1] (maximum number of times the ZVS gradient manifold is cut by even lower dimensional arbitrary plane to disjoint sets): There may be for example at least $2^{180}=1532495540865888858358347027150309183618739122183602176$ maximum number of configurations of electrons corresponding to the complexity of carbon C60 (N=60) assuming the lowest nontrivial folding 2 (parabola-like). We use therefore genetic algorithm to find possible classical Wiger crystal allotropes leading quantum configurations for large number of electrons. We find several distinct configurations for large number of electrons. The genetic operations on configuration spiecies are also discussed. [1] M. Kalinski, L. Hansen, and D. Farrelly, Phys. Rev. Lett. {\bf 95}, 103001 (2005). [Preview Abstract] |
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