Lifetimes and branching ratios of excited states inLa−,Os−,

Steven M. O’Malley

¹

,

Donald R. Beck

²

Abstract

Relativistic configuration-interaction calculations have been performed for all possible E1, M1, and E2 transitions between bound anion states of La − and Os − . We pay particular attention to E1 transitions in each case that may be of use in laser cooling of these anions. Although the La − transition energy is approximately one-third of the Os − 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 − and Lr − which are restricted to M2 decay by selection rules. Finally, in Pr − , we find sufficient mixing between a weakly bound excited 4f 2 5d 2 6s 2 state with a nearby 4f 3 6s 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.

Experimental and theoretical study of bound and quasibound states ofCe−

“…Such bound-bound transitions have been observed previously for only a single atomic negative ion, Os − [6][7][8]. Studies of electric-dipoleallowed transitions take on greater importance with the recent propositions to laser cool negative ions [7][8][9][10][11].…”

Ab initio study of the neutral and anionic alkali and alkaline earth hydroxides: Electronic structure and prospects for sympathetic cooling of OH−

“…Direct laser cooling method are routinely used to reach the utracold regime for neutral and cationic atoms (mostly alkali and alkaline earth) but have so far never been applied to anions even tough some atomic anions such as La − and Os − exhibit stable excited electronic states and represent potential candidates for laser cooling 7,42 . The direct laser cooling of molecules is complicated by the lack of closed transition cycles and requires advanced cooling schemes.…”

Candidates for laser cooling of atomic anions: La−versus Os−

“…In an earlier paper [4], our research group proposed a new candidate for laser cooling, La − , in addition to Os − [3,5]. Comparisons were made [4] between these two anions.…”

“…Comparisons were made [4] between these two anions. For example, the E1 transition in La − has a lower transition energy than that in Os − ( Fig.…”

“…Unlike the previous work [4], the 5d 2 correlation was explicitly introduced in the basis set in this work. The neardegeneracy between the 5d and the 6s electron manifests itself as the mixing of 5d 2 6s6p (∼18%) in La − 5d6s 2 6p 3 D 1 and the mixing of 5d 7 6s6p (∼6%) in Os − 5d 6 6s 2 6p 6 D 9/2 .…”