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 K4: Atomic Spectroscopy |
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Chair: Alex Godunov, Old Dominion University Room: Clark Hall 108 |
Thursday, May 21, 2009 10:30AM - 10:42AM |
K4.00001: Polarizability of Pb III from spectroscopy of high-L Rydberg states of Pb II Mark E. Hanni, Stephen R. Lundeen, William G. Sturrus, Charles W. Fehrenbach Using the Resonant Excitation Stark Ionization Spectroscopy technique[1], we measured resolved fine structure components of the n=20 to n'=52 transition in Pb$^{+}$, and determined the polarizability of Pb$^{2+}$. A critical part of the measurement consists of the determination of the L-value of one or more of the resolved excitation peaks. These measurements were motivated by a discrepancy between previous polarizability determinations based on contrasting methods[2]. [1] S.R. Lundeen and C.W. Fehrenbach, Phys. Rev. A 75, 032523 (2007)[2] Nicholas Reshetnikov, et. al., Physica Scripta 77, 015301 (2008). [Preview Abstract] |
Thursday, May 21, 2009 10:42AM - 10:54AM |
K4.00002: Properties of Ni$^{+}$ from spectroscopy of high-L Rydberg levels of Ni Julie A. Keele, Shannon L. Woods, Mark E. Hanni, Stephen R. Lundeen, William G. Sturrus A single high-L Rydberg electron bound to the $^{2}$D$_{5/2}$ ground state of Ni$^{+}$ leads to a Rydberg fine structure consisting of six levels for each value of L, corresponding to the six possible values of the quantum number K=L+J. The resulting fine structure pattern in n=9, L $>$ 4 levels of Ni was resolved in measurements of the Ni 9-19 and 9-20 transitions, using the Resonant Excitation Stark Ionization Spectroscopy technique [1]. The pattern was analyzed to determine the scalar and tensor polarizabilities and the permanent electric quadrupole moment of Ni$^{+}(^{2}$D$_{5/2})$. [1] E.L Snow, et. al. Phys. Rev. A 71, 022510 (2005) [Preview Abstract] |
Thursday, May 21, 2009 10:54AM - 11:06AM |
K4.00003: Dipole and Quadrupole transition strengths in Ba$^{+}$ from measurements of K-splittings in high-L Ba Rydberg levels Shannon L. Woods, Stephen R. Lundeen, William G. Sturrus, Erica L. Snow Measurements of K-splittings in high-L Rydberg levels of Ba have been used to determine electric dipole (6s-6p) and quadrupole (6s-5d) transition strengths in Ba$^{+}$ [1]. In that report, good agreement with calculated values was found for the dipole strength but not for the quadrupole strength. Using the data pattern extended to higher L levels recently [2] and a more complete theoretical model, we find good agreement between the measured K-splittings and the most recent theoretical calculations of relevant transition strengths.[3] [1] E.S. Shuman and T.F. Gallagher, Phys. Rev. A \underline {74}, 022502 (2006) [2] E.L. Snow, et. al., Phys. Rev. \underline {71}, 022510 (2005) [3] E. Iskrenova-Tchoukova and M. S. Safronova, et. al. Phys. Rev. A \underline {78}, 012508 (2008) [Preview Abstract] |
Thursday, May 21, 2009 11:06AM - 11:18AM |
K4.00004: Electric Quadrupole Moments of Metastable States of Ca$^+$, Sr$^+$, and Ba$^+$ Dansha Jiang, Bindiya Arora, Marianna Safronova Electric quadrupole moments of the metastable $nd_{3/2}$ and $nd_{5/2}$ states of Ca$^+$, Sr$^+$, and Ba$^+$ are calculated using the relativistic all-order method including all single, double, and partial triple excitations of the Dirac-Hartree-Fock wave function to provide recommended values for the cases where no experimental data are available. The contributions of all non-linear single and double terms are also calculated for the case of Ca$^+$ for comparison of our approach with the CCSD(T) results. The third- order many body perturbation theory is used to evaluate contributions of high partial waves and the Breit interaction. The remaining omitted correlation corrections are estimated as well. Extensive study of the uncertainty of our calculations is carried out to establish accuracy of our recommended values to be 0.5\% - 1\% depending on the particular ion. Comprehensive comparison of our results with other theoretical values and experiment is carried out. Our result for the quadrupole moment of the $3d_{5/2}$ state of Ca$^+$ ion, 1.849(17)~$ea_0^2$, is in agreement with the most precise recent measurement 1.83(1)~$ea_0^2$ by Roos et al. [Nature 443, 316 (2006)]. [Preview Abstract] |
Thursday, May 21, 2009 11:18AM - 11:30AM |
K4.00005: The Iron Project and the Rmax Project: Photoionization, Electron-Ion Recombination and Oscillator Strengths of Fe Ions, Fe~XVII and Fe~XXII Anil Pradhan, Sultana Nahar, Werner Eissner The Iron Project and the Rmax Project aim in detail study of radiative and collisional processes of astrophysically abundant atoms and ions, mainly iron and iron-peak elements, over a wide energy range, from infra-red to X-rays. The present work will report oscillator strengths for photo-excitations in Fe~XXII, photoionization cross sections and electron-ion recombination rates for Fe~XVII. The calculations were carried out in relativistic Breit-Pauli approximation. For Fe~XXII, allowed electric dipole, forbidden electric quadrupole, electric octupole, magnetic dipole and magnetic quadrupole transitions will be presented. They represent a set of 771 bound fine structure levels with 1/2 $\leq J \leq$ 17/2. The calculated energy levels were identified spectroscopically using quantum defect analysis. For Fe~XVII, results on photoionization and electron-ion recombination, total and level-specific obtained using the unified method, will be presented from the latest R-matrix calculations using a 60-level wave function expansion. The emphasis of this study is on the features in the high energy and high temperature region. [Preview Abstract] |
Thursday, May 21, 2009 11:30AM - 11:42AM |
K4.00006: Soft X-ray Spectra of Highly Charged Hf, Ta, W, and Au Joseph Reader, John Gillaspy, Ilija Draganic, Yuri Ralchenko, Joseph Tan, Joshua Pomeroy, Samuel Brewer We use our EBIT to measure wavelengths for highly-charged states of heavy elements for use in diagnostics of fusion-type plasmas, such as ITER. The range of our grazing-incidence spectrometer has been extended to below 2 nm to obtain overlap with our microcalorimeter. Our range of electron impact energies now spans 2-24 keV. We use atomic data generated by the FAC code and collisional-radiative modeling with the NOMAD code to interpret the observed spectra. Previously [1], we published wavelengths for Na-like, Mg-like, and Al-like ions of Hf(Z=72), Ta(Z=73), W(Z=74), and Au(Z=79) from 6.5 to 8.5 nm. We now measure wavelengths for these ions in the region 1.8 to 2.6 nm. Our preliminary values for the 3s$_{1/2}$-3p$_{3/2}$ transition in the Na-like ions are 2.5772(18) nm for Hf$^{61+}$, 2.4498(18) nm for Ta$^{62+}$, 2.3245(18) nm for W$^{63+}$, and 1.8059(22) nm for Au$^{68+}$. For these ions, the fine structure splitting of the D-line doublet is larger than the mean value of the transition energy. We observe this giant splitting directly in a single spectrum on our grazing-incidence spectrometer. [1]Yu. Ralchenko et al., J. Phys. B: At. Mol. Opt. Phys. \textbf{41}, 021003 (2008). [Preview Abstract] |
Thursday, May 21, 2009 11:42AM - 11:54AM |
K4.00007: Studies of the Coster-Kronig, Shake off probabilities and Gaussian curves of L X-Ray satellites spectra Surendra Poonia The X-ray satellite spectra arising due to L$_{2}$M$_{x}$-M$_{x}$M$_{4,5}$, L$_{3}$M$_{x}$-M$_{x}$M$_{4,5 }$and L$_{3}$M$_{x}$-M$_{x}$N$_{4,5}$ (x $\equiv $ 1-5) transition array, in elements with Z = 26 to 92, have been calculated, using available Hartree-Fock-Slater (HFS) data on K-L$_{3}$M$_{x}$ and L$_{3}$-M$_{x}$M$_{4,5}$ 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 L$_{3}$M$_{x}$ amongst various allowed transitions from these initial states to M$_{x}$M$_{4,5}$ final states by Coster-Kronig (CK) and shake off processes. In both these processes, initial single hole creation is the prime phenomenon and electron bombardment has been the primary source of energy. 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$\alpha _{1}$ L$\beta _{1}$ and L$\beta _{2}$ spectra. The one to one correspondence between the peaks in calculated spectra and the satellites in measured spectra has been established on the basis of the agreement between the separations in the peak energies and those in the measured satellite energies. 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 L$\alpha _{3}$, L$\alpha _{4}$, L$\alpha _{5}$, L$\alpha \prime $, L$\alpha ^{ix}$,$^{ }$L$\alpha ^{x}$, L$\beta _{1}^{I}$, L$\beta _{1}^{II}$, L$\beta _{1}^{III}$, L$\beta _{1}^{IV}$ L$\beta _{2}^{I}$, L$\beta _{2}^{(b)}$, L$\beta _{2}^{II}$ and L$\beta _{2}^{(c)}$ which lie on the high-energy side of the L$\alpha _{1}$, L$\beta _{1}$, L$\beta _{2}$ dipole line. [Preview Abstract] |
Thursday, May 21, 2009 11:54AM - 12:06PM |
K4.00008: Theoretical shapes of L$\alpha_{1}$ X-Ray satellites spectra of 4d transition elements by HFS calculations Poonia Surendra 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. In both these processes initial single hole creation is the prime phenomenon and electron bombardment has been the primary source of energy. 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, May 21, 2009 12:06PM - 12:18PM |
K4.00009: Indirect spin-orbit K splittings in strontium Jirakan Nunkaew, Edward Shuman, Thomas Gallagher We use delayed field ionization to observe the resonance transitions of Sr from $5snf$ to $5sng$, $5snh$ and $5sni$. Each resonance transition is split by the indirect spin-orbit coupling, K splitting, of the Sr core. From the K splitting we extract the ionic dipole and quadrupole matrix, $\langle5s\vert r\vert 5p\rangle=3.65(25)$a$_0$ and $\langle5s\vert r^2\vert4d\rangle =12(8)$a$_0^2$, respectively. We use the dipole matrix element to obtain the dipole polarizability of Sr$^+$. We determine the quadrupole polarizability of Sr $^+$ by the use of dipole polarizability and the quantum defect differences of the adjacent $\ell$ states. This work has been supported by the U.S. Department of Energy, Office of Basic Energy Sciences. [Preview Abstract] |
Thursday, May 21, 2009 12:18PM - 12:30PM |
K4.00010: Hydrogen and Helium atoms in strong magnetic fields Anand Thirumalai, Jeremy Heyl The energy levels of hydrogen and helium atoms in strong magnetic fields are calculated in this study. The current work contains accurate estimates of the binding energies of the first few low-lying states of these systems that are improvements upon previous estimates. The methodology involves computing the eigenvalues and eigenvectors of the generalized two-dimensional Hartree-Fock partial differential equations for these one- and two-electron systems in a self-consistent manner. The method described herein is applicable to calculations of atomic structure in magnetic fields of arbitrary strength as it exploits the natural symmetries of the problem without assumptions of any basis functions for expressing the wave functions of the electrons or the commonly employed adiabatic approximation. The method is found to be readily extendable to systems with more than two electrons. [Preview Abstract] |
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