Properties of the Low-Lying Electronic States of the ThH and ThH+ Molecules: A Theoretical Investigation Includes Spin-Orbit Coupling.

The spectroscopic properties of electronic states of ThH and ThH+ molecules are investigated in our work using the high-level ab initio calculation. The potential energy curves (PECs) of 6 Λ-S states of ThH and 9 Λ-S states of ThH+, which come from the first and second dissociation channels, as well as 10 Ω states of ThH and 21 Ω states of ThH+ considering the spin-orbit coupling (SOC) effect, are determined, and the spectroscopic constants are also obtained. Additionally, the dipole moments (DMs) and the transition dipole moments are calculated. Based on the computed PECs, the Franck-Condon factors (FCFs) of the A2 Δ-X2Π and a3 Δ1 - X1 Σ0+ transitions are found to be highly diagonal. However, the radiative lifetimes of the A2 Δ-X2Π and a3 Δ1 - X1 Σ0+ transitions are calculated to be on the order of ms, which indicate the impossibility of direct laser-cooling ThH and ThH+ molecules.