Lifetimes and branching ratios of excited states inLa−,Os−,Lu−,Lr−, andPr−

Abstract

Relativistic configuration-interaction calculations have been performed for all possible $E1$, $M1$, and $E2$ transitions between bound anion states of ${\mathrm{La}}^{\ensuremath{-}}$ and ${\mathrm{Os}}^{\ensuremath{-}}$. We pay particular attention to $E1$ 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 $A$ 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 ${\mathrm{Lu}}^{\ensuremath{-}}$ and ${\mathrm{Lr}}^{\ensuremath{-}}$ which are restricted to $M2$ decay by selection rules. Finally, in ${\mathrm{Pr}}^{\ensuremath{-}}$, we find sufficient mixing between a weakly bound excited $4{f}^{2}5{d}^{2}6{s}^{2}$ state with a nearby $4{f}^{3}6{s}^{2}6p$ 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.