Bulletin of the American Physical Society
38th Annual Meeting of the Division of Atomic, Molecular, and Optical Physics
Volume 52, Number 7
Tuesday–Saturday, June 5–9, 2007; Calgary, Alberta, Canada
Session H6: Atomic Structure and Spectroscopy |
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Chair: J. Delos, College of William and Mary Room: TELUS Convention Centre Olde Scotch Room |
Thursday, June 7, 2007 10:30AM - 10:42AM |
H6.00001: Spectroscopy of Atomic Systems under Plasma Environment Amar Nath Sil, S. Fritzsche, P. K. Mukherjee Extensive model calculations have been performed to study the effect of plasma on the structural properties like ground and excited energy levels, dipole polarizabilities, oscillator strengths, transition probabilities of hydrogen and helium like systems. For weak coupling case Debye screening model and for strong coupling case Ion Sphere model of the plasma have been applied. We studied in particular the hydrogen like carbon, aluminium and argon and helium like carbon under different plasma coupling strengths. Time dependent linear response theory has been utilized in finding the excitation properties of the ionic systems under such plasma conditions. The spectral line shifts have been calculated and ionization pressure has been estimated using finite boundary conditions imposed on the wave functions. It is noted that with finite plasma coupling the ionization potential decreases and the number of excited states become finite. The system approaches towards instability gradually as the strength of the coupling is increased. Theoretical estimates of the spectral line positions under such plasma for several hydrogen like systems seem to be in very good agreement with the experimental observations with laser produced plasmas. [Preview Abstract] |
Thursday, June 7, 2007 10:42AM - 10:54AM |
H6.00002: Relativistic coupled-cluster single-double method applied to alkali-metal atoms Rupsi Pal, M.S. Safronova, W.R. Johnson, Andrei Derevianko, Sergey G. Porsev A relativistic version of the coupled-cluster single-double (CCSD) method is developed for atoms with a single valence electron. In earlier work, a linearized version of the CCSD method (with extensions to include a dominant class of triple excitations) led to accurate predictions for energies, transition amplitudes, hyperfine constants, and other properties of monovalent atoms. Further progress in high-precision atomic structure calculations for heavy atoms calls for improvement of the linearized coupled-cluster methodology. In the present work, equations for the single and double excitation coefficients of the Dirac-Fock wave function, including all non-linear coupled-cluster terms that contribute at the single-double level are worked out. Contributions of the non-linear terms to energies, electric-dipole matrix elements, and hyperfine constants of low-lying states in alkali-metal atoms from Li to Cs were systematically investigated. The effect of the core non-linear terms was found to be not negligible for heavier alkalies, reaching nearly 1\% of the total values of the Cs hyperfine constants. The final results are compared with other calculations and with precise experiments. [Preview Abstract] |
Thursday, June 7, 2007 10:54AM - 11:06AM |
H6.00003: Excitation energies, hyperfine constants, transition rates, and lifetimes of $5s^2nl$ states in In~I and Sn~II U.I. Safronova, M.S. Safronova, M.G. Kozlov Energies of $5s^2np_j$ ($n$ = 5--8), $5s^2ns_{1/2}$ ($n$ = 6-- 9), $5s^2nd_j$ ($n$ = 5--8), and $5s^2nf_{j}$ ($n$ = 4--5) states in In~I and Sn~II are obtained using relativistic many-body perturbation theory. Reduced matrix elements, oscillator strengths, transition rates, and lifetimes are determined for the 102 possible $5s^2nl_j-5s^2n'l'_{j'}$ electric-dipole transitions. Electric-quadrupole and magnetic-dipole matrix elements are evaluated to obtain $5s^25p_{3/2} - 5s^25p_{1/2}$ transition rates. Hyperfine constants $A$ are evaluated for $5s^2np_j$ ($n$ = 5--8), $5s^2ns_{1/2}$ ($n$ = 6--9), and $5s^2nd_j$ ($n$ = 5--8) states in $^{115}$In and $^{113}$In. First-, second-, third-, and all-order corrections to the energies and matrix elements and first- and second-order Breit corrections to energies are calculated. In our implementation of the all- order method, single and double excitations of Dirac-Fock wave functions are included to all orders in perturbation theory. These calculations provide a theoretical benchmark for comparison with experiment and theory. [Preview Abstract] |
Thursday, June 7, 2007 11:06AM - 11:18AM |
H6.00004: Spectroscopy of $^1$S$_0 \leftrightarrow ^3$P$_0$ transition in In$^+$ William Trimble, Warren Nagourney We report spectroscopy of the $^1$S$_0 \leftrightarrow ^3$P$_0$ transition at 237~nm in single indium ions confined in a Paul- Straubel trap. The indium ion is among candidates for optical frequency references because of the high quality factor (Q $\sim 1.5 \cdot 10^{15}$) and the small quadrupole and blackbody shifts of its ground-state to $^3$P$_0$ transition. Using a frequency- quadrupled diode laser to cool the ion on the stronger $^1$S$_0 \leftrightarrow ^3$P$_1$ transition, we report sub-kHz linewidths in exciting the narrow $^3$P$_0$ transition using a frequency-quadrupled Nd:YAG nonplanar ring oscillator (NPRO) at 946~nm stabilized to a vertically-mounted high-finesse ULE cavity. [Preview Abstract] |
Thursday, June 7, 2007 11:18AM - 11:30AM |
H6.00005: 2p$_{3/2}^{-1}$3x$^{-1}$-3x$^{-1}$3d$^{-1}$ X-Ray satellites in the L$\alpha_{1}$ spectra of 4d transition elements Surendra Poonia The X-ray satellite spectra arising due to 2p$_{3/2}^{-1}$3x$^{-1}$-3x$^{-1}$3d$^{-1}$ (x $\equiv $ s, p, d) transition array, in elements with Z = 40 to 48, have been calculated, using available Hartree-Fock-Slater (HFS) data on 1s$^{-1}$-2p$^{-1}$3x$^{-1}$ and 2p$_{3/2}^{-1}$-3x$^{-1}$,3x'$^{-1}$ Auger transition energies. The relative intensities of all the possible transitions have been estimated by considering cross - sections for the Auger transitions simultaneous to a hole creation and then distributing statistically the total cross sections for initial two hole states 2p$_{3/2}^{-1}$3x$^{-1}$ amongst various allowed transitions from these initial states to 3x$^{-1}$3d$^{-1}$ final states by Coster-Kronig (CK) and shake off processes. Each transition has been assumed to give rise to a Gaussian line and the overall spectrum has been computed as the sum of these Gaussian curves. The calculated spectra have been compared with the measured satellite energies in L$\alpha _{1}$ spectra. Their intense peaks have been identified as the observed satellite lines. The peaks in the theoretical satellite spectra were identified as the experimentally reported satellites $\alpha _{3}$, $\alpha _{4}$ and $\alpha _{5}$, which lie on the high-energy side of the L$\alpha _{1}$ dipole line. [Preview Abstract] |
Thursday, June 7, 2007 11:30AM - 11:42AM |
H6.00006: Relativistic nuclear recoil, electron correlation and QED effects in highly charged Ar ions Z. Harman, R. Soria Orts, A. Lapierre, J.R. Crespo Lopez-Urrutia, A.N. Artemyev, I.I. Tupitsyn, U.D. Jentschura, C.H. Keitel, H. Tawara, J. Ullrich, V.M. Shabaev, A.V. Volotka We have performed extensive theoretical studies on the 1s$^{2}$2s$^{2}$2p$^{2}$P$_{3/2}$ -- $^{2}$P$_{1/2}$ M1 transition in Ar${}^{13+}$ ions. Accurate radiative lifetimes are sensitive to QED corrections like the electron anomalous magnetic moment and to relativistic electron correlation effects. The lifetime of the P$_{3/2}$ metastable state was determined to be 9.573(4)(5) ms (stat)(syst) [1] using the Heidelberg electron beam ion trap. Theoretical predictions cluster around a value that is significantly shorter than this high-precision experimental result. This discrepancy is presently unexplained. The wavelengths of the above transition in Ar$^{13+}$ and the 1s$^{2}$2s2p $^{3}$P$_{1}$ -- $^{3}$P$_{2}$ M1 transition in Ar$^{14+}$ were compared for the isotopes $^{36}$Ar and $^{40}$Ar [2]. The observed mass shift has confirmed the relativistic theory of nuclear recoil effects in many-body systems. Our calculations, based on the fully relativistic recoil operator, are in excellent agreement with the measured results. [1] A. Lapierre, U.D. Jentschura, J.R. Crespo L\'{o}pez-Urrutia {\it et al.}, Phys. Rev. Lett. 95, 183001 (2005); [2] R. Soria Orts, Z. Harman, J.R. Crespo L\'{o}pez-Urrutia {\it et al.}, Phys. Rev. Lett. 97, 103002 (2006) [Preview Abstract] |
Thursday, June 7, 2007 11:42AM - 11:54AM |
H6.00007: Modeling and Spectroscopic Analysis of non-LTE Krypton Plasmas Arati Dasgupta, R.W. Clark, Y.K. Chong, J. Davis We have developed a detailed multilevel atomic model for K-, L- and M-shell krypton, and investigated its impact on the radiation hydrodynamics on a krypton gas puff driven by the redesigned Sandia National Laboratory ZR accelerator. The atomic model employs an extensive atomic level structure, which is necessary to accurately model the pinch dynamics and the spectroscopic details of the emitted radiation. The atomic data was obtained using the state-of-the-art Flexible Atomic Code, and all relevant radiative atomic processes were included in generating the model. The enormous number of fine-structure levels were judiciously lumped to create a database that is detailed but manageable. We have analyzed the behavior in the krypton K- through M-shell ionization stages using temperature and density conditions that have been predicted in 1-D and 2-D MHD calculations of implosions on ZR. [Preview Abstract] |
Thursday, June 7, 2007 11:54AM - 12:06PM |
H6.00008: Absorption Lineshape Modeling of Neutral Xenon in a Magnetized Optogalvanic Cell. Bailo Ngom, Tim Smith, Alec Gallimore We present a computational model for Zeeman splitting of the $6s ^2[3/2]^1_0 \to 6p\ ^2[5/2]_2$ absorption of neutral xenon at 834.682 nm (air). The model accounts for Zeeman splitting of the xenon hyperfine structure by assuming that the extra-nuclear spin and spin-orbit wavefunctions are separable for an atomic system described by a rigid spherical spinning body in a central force field, all immersed in a magnetic field. This theoretical approach [1] permits calculation of the intensity and displacement of Zeeman-shifted hyperfine lines for $\sigma$ and $\pi$ beam polarizations. By comparing the resulting model with previously-reported Zeeman-split optogalvanic spectra [2], we explore the utility of Zeeman splitting of laser-induced fluorescence spectra as a magnetic component intensity diagnostic in xenon electrostatic thruster plumes. \newline \newline [1] Bacher, R. F. {\em The Zeeman Effect of Hyperfine Structure,} Ph.D. dissertation, University of Michigan, 1930. \newline [2] Smith, T.B., Ngom, B.B., Linnell, J.A., and Gallimore, A.D. \newblock ``Optogalvanic Spectroscopy of the Zeeman Effect in Xenon,'' ICOPS-2006. [Preview Abstract] |
Thursday, June 7, 2007 12:06PM - 12:18PM |
H6.00009: Fast-ion-beam laser-induced-fluorescence measurements of oscillator strengths in doubly ionized lanthanides Ruohong Li, Richard A. Holt, S. David Rosner Accurate oscillator strength data for singly and doubly ionized lanthanides are needed in astrophysics to study the spectra of Chemically Peculiar (CP) stars, which show large overabundances of lanthanides compared to the Standard Abundance Distribution, and for nucleosynthesis studies. We have previously measured oscillator strengths in Sm~II, Nd~II, and Pr~II using fast-ion-beam laser-induced-fluorescence methods. Our new Penning Ion Source provides us doubly-ionized ion beams to study lifetimes and branching fractions of lanthanide ions, which are actually the more abundant charge species in hot CP stars. A new GaAs photomultiplier tube gives us a greater wavelength range (185-930nm) for the detection of spontaneous emission. A new detector-substitution method of detector calibration will make the experimental accuracy significantly below 10{\%}. Recent results will be presented. [Preview Abstract] |
Thursday, June 7, 2007 12:18PM - 12:30PM |
H6.00010: DAVLL with Frequency Markers Frank A. Narducci, Ethan R. Elliott, Christopher J. Lehman The Dichroic Atomic Vapor Laser Lock (DAVLL) technique for locking lasers to atomic transitions has the advantage of a large capture range but the disadvantage that there are no convenient frequency markers to know very well where a laser is tuned relative to atomic transitions. On the other hand, saturated absorption spectroscopy has the frequency markers, but not the large capture range. We present a simple, compact scheme that combines the advantages of both techniques. Spectral measurements in all four Doppler absorption lines of Rubidium will be presented, showing a very rich structure with multiple features that can be used either as frequency references or additional frequency locking. The underlying physics of these features are sorted out and identified. Of particular use to the laser-cooling community is a large cross-over resonance that occurs right at the location of the cooling resonance independent of the strength of the magnetic field used to generate the DAVLL signal. [Preview Abstract] |
Thursday, June 7, 2007 12:30PM - 12:42PM |
H6.00011: Planetary multi-electron atoms as fully controled Wigner crystal clusters Matt Kalinski We consider highly excited multi-electron atoms in both the circularly polarized and the strong magnetic fields. Following our work on the two electron Langmuir configurations [1] we discover that a variety of static electron configurations is possible for $n$-electrons for $Z_n$ charged ions. The simplest originate from the Jupiter ring or the Kuiper belt-like configurations. Those configuratios may exhibit highly exotic stability islands, when the Lyapunov coefficients for classical trajectories are purely imaginary numbers. Those stability islands may be considered as discrete transitions to multidimensional variables of the Cantor set describing the mass distribution in Kuiper belt and the Jupiter ring. \newline [1] M. Kalinski, L. Hansen and D. Farrelly, Phys. Rev. Lett. 95, 103001-1, (2005). [Preview Abstract] |
Thursday, June 7, 2007 12:42PM - 12:54PM |
H6.00012: Monodromy and the Structure of the Spectrum of the Hydrogen Atom in Near Perpendicular Electric and Magnetic Fields Christopher Schleif, John Delos We study the hydrogen atom in weak perpendicular and near-perpendicular electric and magnetic fields using quantum and classical perturbation theory. Classical perturbation theory provides an integrable approximation to trajectories, providing three approximate constants of the motion. Quantization of actions produces a lattice of semiclassical expectation values which is in good agreement with direct quantum calculations. For certain ranges of electric and magnetic field strengths and orientations the lattice contains defects connected with a subtle phenomenon of classical mechanics called monodromy. If a classical system has monodromy then there is a classical action variable which is an intrinsically multivalued function of the constants of the motion. Monodromy had been predicted to be present for perpendicular fields by Sadovski\'{\i} and Cushman. We show that the presence of monodromy persists in near-perpendicular fields, and that the associated lattice defects undergo a series of bifurcations. We have used classical mechanics to map out the range of lattice structure in all weak near-perpendicular field configurations from the Stark to Zeeman limits. We show that there are six different families of spectra, five of which display the effects of monodromy. [Preview Abstract] |
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