Steven M. O'Malley

Lifetimes and branching ratios of excited states in La-, Os-, Lu-, Lr-, and Pr-

Relativistic configuration-interaction calculations have been performed for all possible E1, M1, and E2 transitions between bound anion states of La{sup -} and Os{sup -}. We pay particular attention to E1 transitions in each case that may be of use in laser cooling of these anions. Although the La{sup -} transition energy is approximately one-third of the Os{sup -} transition, our results indicate that the Einstein A coefficient is nearly two orders of magnitude larger, which would lead to more efficient laser cooling. We have also explored long-lived opposite-parity excited states in Lu{sup -} and Lr{sup -} which are restricted to M2 decay by selection rules. Finally, in Pr{sup -}, we find sufficient mixing between a weakly bound excited 4f{sup 2}5d{sup 2}6s{sup 2} state with a nearby 4f{sup 3}6s{sup 2}6p resonance to result in a lifetime similar to that of the other excited anion states, despite the fact that the dominant configurations of these M1 and E2 transitions differ by two electrons.

Calculation of Ce^- binding energies by analysis of photodetachment partial cross sections (10 pages)

The electron affinity of cerium is determined from relativistic configuration interaction photodetachment calculations through a reinterpretation of available experimental data [V. T. Davis and J. S. Thompson, Phys. Rev. Lett. 88, 073003 (2002)]. This analysis yields a 4f5d{sup 2}6s{sup 2} {sup 4}H{sub 7/2} Ce{sup -} ground state (a 5d attachment relative to the 4f5d6s{sup 2} {sup 1}G{sub 4} neutral Ce ground state) with binding energy of 0.660 eV as well as 18 other bound states of the same configuration. The lowest-lying state of seven bound states of the opposite parity (6p attachments) is 4f5d6s{sup 2}6p {sup 2}H{sub 9/2}, which is bound by 0.300 eV.

Oscillator strengths, Landégvalues, and hyperfine structure for3d4J=0→3d34pJ=1transitions in Fe V

Relativistic configuration-interaction (RCI) calculations with {approx}15000 vectors have been done for f values, Lande g values, and hyperfine structure constants for Fe V. There is at least a factor of 2 improvement over our earlier achievable accuracies (Nb II). The 21 largest f values (>0.01) have an average length-velocity gauge difference of 6.7%, and the average error in the energy differences between adjacent levels is 213 (180) cm{sup -1} for even- (odd-) parity levels. We find significant f value differences as compared to recent values from Breit-Pauli R-matrix calculations, and, to a lesser extent, as compared to older semiempirical f values. Oscillator strengths to three nearly degenerate odd-parity levels are sensitive to errors smaller than 200 cm{sup -1}, but the sum is conserved, as expected.

Removal or excitation of a 1s electron in Kr II and Kr III

Relativistic configuration interaction calculations are done for Kr ions Kr II and Kr III. Transition energies and transition probabilities for 122 transitions between Kr II 4p5 J = 1/2, 3/2→ 1s 4p6, 1s 4p5 np (n = 5–8) J = 1/2, 3/2, 5/2; 437 transitions between Kr III 4p4 J = 0, 1, 2→ 1s 4p5, 1s 4p4 np (n = 5–8) J = 0, 1, 2, 3 have been calculated. These data have been used by experiment to reproduce the absorption spectrum of Kr II and Kr III and found to be in good agreement with their measurement. Also, the K-edge energy of neutral Kr, Kr II and Kr III has been calculated. The first is within 0.94 eV of an existing experiment, while the last two are calculated for the first time.

Autodetachment lifetime calculations of long-lived metastable states of Ba− and Eu−

A calculation of the autodetachment energy width of the decay of the Ba− 5d6s6p 4F9/2 metastable state to the 6s2h9/2 continuum predicts a lifetime for this state of 0.19 s. The Ba− calculation is used as a template for the more computationally intensive calculation of the analogous 4f75d6s6p J = 8 metastable state of Eu−. This state is predicted to lie 11 797 cm−1 above the 4f76s2 Eu I ground state with a lifetime of 0.23 s. Opening of the 5p subshell in both cases and careful treatment of cancellation in the energy width calculations have been essential in obtaining these lifetimes.

Improved RCI techniques for atomic 4f{\hspace*{1.5pt}}^n excitation energies: application to Sm I 4f{\hspace*{2pt}}^66s2 5DJ levels

We complete the development of a relativistic energy-dependent efficient method by which important pair-correlation effects associated with open subshells can be incorporated into the relativistic configuration interaction (RCI) methodology. We apply this to predict the positions of the 4f6s2 5DJ levels of Sm I. Relative to 5D1, we predict 5D0 lies at −1613 cm−1 and 5D4 at 6589 cm−1. For 5D2 and 5D3, we are 22 cm−1 and 123 cm−1 below the observed difference, respectively. We also calculate magnetic dipole transition rates among these levels and the ground-state 7FJ levels, which may be of interest to future parity nonconservation studies.

Relativistic configuration interaction calculations of electron affinities for three bound states of Lu- formed by 6p attachment

Valence shell relativistic configuration interaction calculations indicate three bound states for Lu- by 6p attachment to the 5d6s2 J = 3/2 ground state. These include two J = 2 levels with electron affinities of 329 and 124 meV, as well as one J = 3 level at 63 meV. The first value is 139 meV larger than the previously published value, while the latter two are predicted here for the first time. We find second-order effects moderately important in the binding of these states, while certain core excitations (particularly involving the 4f subshell) were found to have a negligible impact.