Theoretical investigation for the laser cooling of LuH+ molecular cation

The potential energy curves and transition dipole moments of seven Λ-S states and six Ω states of LuH+ cation are calculated by using the multireference configuration interaction method plus Davidson correction with the pseudopotential electron basis set, and the spectroscopic parameters of the bound states are obtained. The spin–orbit coupling effect is considered in the calculations. The Franck–Condon factors (FCFs) and the Einstein spontaneous emission coefficients are obtained. The results indicate that the A2Δ3/2(ν′ = 0) ↔ X2Σ+1/2(ν″ = 0) and B2Π1/2(ν′ = 0) ↔ X2Σ+1/2 (ν″ = 0) transitions provide highly diagonally distributed FCFs. Spontaneous radiative lifetimes of A2Δ3/2 (ν′ = 0) and B2Π1/2 (ν′ = 0) excited states are both obtained. The cooling schemes of LuH+ cation are obtained using the ab initio method. For the B2Π1/2 ↔ X2Σ+1/2 transition, the influence of the intermediate state on the construction of quasi-closed cyclic transitions can be neglected. A main pump laser and two repumping lasers are required to construct the A2Δ3/2 ↔ X2Σ+1/2 and B2Π1/2 ↔ X2Σ+1/2 quasi-cycling transitions for laser cooling of LuH+ molecular cation. The results in this work provide reliable theoretical guidance for further experiments of laser cooling of LuH+ cation.