Effects of spin-orbit coupling on laser cooling of BeI and MgI

We present the ab initio study of spin-orbit coupling effects on laser cooling of BeI and MgI molecules. Potential energy curves for the X²Σ⁺_1/2, A²Π_1/2,3/2, and 2²Π_3/2,1/2 states are calculated using multi-reference configuration interaction method plus Davidson corrections. Spectroscopic parameters of BeI and MgI are in excellent agreement with available experimental and theoretical values. The A²Π_3/2 state of MgI is a repulsive state. It is an unsuitable scheme for the A²Π_3/2(υ′)← X²Σ⁺_1/2 (υ″) transition for laser cooling of MgI. Highly diagonally distributed Franck-Condon factors f₀₀ for the A²Π_1/2,3/2 (υ′ = 0) ← X²Σ⁺_1/2 (υ″ = 0) transitions and suitable radiative lifetimes τ for the A²Π_1/2,3/2 (υ′ = 0) of BeI and MgI are obtained. Three laser wavelength drives are required for the A²Π_1/2,3/2(υ′)←X²Σ⁺_1/2 (υ″) transitions of BeI and MgI. The proposed cooling wavelengths of BeI and MgI are both in the violet region. The results imply the feasibility of laser cooling of BeI and MgI, and that laser cooling of BeI is more possible