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.