Laser cooling and electronic structure of Be halide anions BeX^- (X = Cl, Br, F, and I)

The adiabatic potential energy curves of the low lying electronic states of the Be halide anions BeX^- (Cl, Br, F, and I) have been investigated in the representation ^2s+1Λ^(+/-) by using the complete active space self-consistent field with a multireference configuration interaction method. The spectroscopic parameters T_e, R_e, ω_e, and B_e and the static and transition dipole moment μ_e were studied, and a rovibrational study of the investigated electronic states was performed. New electronic states were investigated here for the first time. The calculated highly diagonal Franck-Condon factor and the short radiative lifetime among the lowest vibrational levels of the X¹Σ₀₊ - (1)³Π₁ transitions of the molecular anion BeF^- prove its candidacy for Doppler laser cooling. The experimental proof of the stability and the calculated experimental parameters, such as the vibrational branching ratio, the slowing distance, the recoil, and Doppler temperatures with the experimental conditions of the buffer gas cell of this anion, open the route for experimental work on the BeF^- molecular ion.