Laser cooling of MgCl and MgBr in theoretical approach

Ab initio calculations for three low-lying electronic states (X²Σ⁺, A²Π, and 2²Π) of MgCl and MgBr molecules, including spin-orbit coupling, are performed using multi-reference configuration interaction plus Davidson correction method. The calculations involve all-electronic basis sets and Douglas–Kroll scalar relativistic correction. Spectroscopic parameters well agree with available theoretical and experimental data. Highly diagonally distributed Franck-Condon factors f₀₀ for A²Π_3/2,1/2 (υ′ = 0) → X²Σ⁺_1/2 (υ″ = 0) are determined for both MgCl and MgBr molecules. Suitable radiative lifetimes τ of A²Π_3/2,1/2 (υ′ = 0) states for rapid laser cooling are also obtained. The proposed laser drives A²Π_3/2 (υ′ = 0) → X²Σ⁺_1/2 (υ″ = 0) transition by using three wavelengths (main pump laser λ₀₀; two repumping lasers λ₁₀ and λ₂₁). These results indicate the probability of laser cooling MgCl and MgBr molecules