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Physical Review A

Electron affinities of 6pelectrons in Pr−

Konstantin D. Dinov, Donald R. Beck

Published Feb 1, 1995• 18 citations
Publisher

Abstract

Valence shell relativistic configuration-interaction calculations for 6p attachments to the Pr ground state yield two bound states for the configuration 4${\mathit{f}}^{3}$6${\mathit{s}}^{2}$6p. The two levels (J) and their electron affinities (EA) are (J, EA (eV))=(4, 0.110) and (5, 0.128). We were unable to find any evidence for 5d or 4f attachments. These results are consistent with the relatively modest experimental yields obtained for ${\mathrm{Pr}}^{\mathrm{\ensuremath{-}}}$.

DOI
10.1103/physreva.51.1680

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The electron affinities of the ground states of Sr and Ba have been calculated using a finite-element multiconfiguration Hartree-Fock method. The valence correlation value for the electron affinity of Sr is 135 meV. Core-valence correlation reduces the electron affinity by 121 meV. By adding relativistic and core-core correlation contributions, the final binding energies of 16 and -6 meV are obtained for Sr -(2) P (1 2)/ and Sr -(2) P (3 2)/, respectively. For Ba, the valence limit is 279 meV, and the core-valence correlation correction is -144 meV. The final binding energies of 113 and 56 meV are obtained for Ba -(2) P (1 2)/ and Ba -(2) P (3 2)/ by adding relativistic and core-core correlation corrections to the core-valence correlation value.
Accurate eigenvalues of Schr\"odinger's nonrelativistic equation for Be (1${s}^{2}2s2p2s2p2s2p{)}^{3}$P and ${\mathrm{Be}}^{\mathrm{\ensuremath{-}}}$ (1${s}^{2}2s22s22s2{p}^{2}$)4{)}^{4})4P have been calculated yielding a corresponding electron affinity A of 276.1\ifmmode\pm\else\textpm\fi{}6.5 meV. The absolute term value of ${\mathrm{Be}}^{\mathrm{\ensuremath{-}}}$ (relative to the Be ground state) obtained as the difference between the experimental term value of Be 3P^{3}\mathrm{P}3P and A is 2.4492\ifmmode\pm\else\textpm\fi{}0.0065 eV, in agreement with a recent measurement of 2.53\ifmmode\pm\else\textpm\fi{}0.11 eV.
We calculate, including many-body effects, that the three lowest bound states of ${\mathrm{Mg}}^{\ensuremath{-}}$, $2{p}^{6}3s3{p}^{2}^{4}P$, $2{p}^{6}3{p}^{3}^{4}S^{0}$ and $2{p}^{5}3s3{p}^{3}^{6}P$, have electron affinities 0.360, 0.514, and 1.321 eV, respectively. The transition $3s3{p}^{2}^{4}P\ensuremath{\rightarrow}3{p}^{3}^{4}S^{0}$ is found to have an electric dipole oscillator strength of 0.295. The lifetimes of the J=12,32,and52J=\frac{1}{2}, \frac{3}{2}, \mathrm{and} \frac{5}{2}J=21​,23​,and25​, 4P^{4}P4P levels are estimated to be 7.8, 9.8, and 1.6 ns, respectively.
Relativistic configuration-interaction calculations have been performed for all possible E1E1E1, M1M1M1, and E2E2E2 transitions between bound anion states of ${\mathrm{La}}^{\ensuremath{-}}$ and ${\mathrm{Os}}^{\ensuremath{-}}$. We pay particular attention to E1E1E1 transitions in each case that may be of use in laser cooling of these anions. Although the ${\mathrm{La}}^{\ensuremath{-}}$ transition energy is approximately one-third of the ${\mathrm{Os}}^{\ensuremath{-}}$ transition, our results indicate that the Einstein AAA 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 ${\mathrm{Lu}}^{\ensuremath{-}}$ and ${\mathrm{Lr}}^{\ensuremath{-}}$ which are restricted to M2M2M2 decay by selection rules. Finally, in ${\mathrm{Pr}}^{\ensuremath{-}}$, we find sufficient mixing between a weakly bound excited 4f25d26s24{f}^{2}5{d}^{2}6{s}^{2}4f25d26s2 state with a nearby 4f36s26p4{f}^{3}6{s}^{2}6p4f36s26p resonance to result in a lifetime similar to that of the other excited anion states, despite the fact that the dominant configurations of these M1M1M1 and E2E2E2 transitions differ by two electrons.
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