Ab Initio Study on the Electronic Structure and Spectroscopic Properties of Lanthanum Monohydride (LaH)

The electronic structure of the 12 Λ-S low-lying electronic states and their corresponding Ω states of LaH was studied using the multireference configuration interaction method with Davidson correction (MRCI+Q). Furthermore, the permanent dipole moments (PDMs) and the electronic transition dipole moments (TDMs) among the low-lying electronic states were calculated as well. Based on the aforementioned results, we calculated the Franck–Condon factors and spontaneous radiative lifetimes for relevant excited states. Theoretical calculations show that LaH exhibits multiple transitions with highly diagonal Franck–Condon factors; however, it is not a promising candidate for laser cooling research. These arise from (1) long excited-state radiation lifetime and (2) non-negligible branching ratio to intermediate electronic states.