Structural investigation for the low-lying electronic states with rovibrational calculations of the alkaline-earth fluoride cations XF⁺ (X = Be, Mg, Ca)

Due to the lack of theoretical data about the electronic structure on the molecular cations BeF⁺, MgF⁺ and CaF⁺, an accurate ab initio calculations have been investigated for these molecules using the multi-reference configuration interaction plus Davidson correction (MRCI + Q) method. The potential energy curves (PECs) of the low-lying electronic states in the representation ^2s+1Ʌ^(+/-) of the three alkaline-earth fluoride cations have been computed. The spectroscopic constants T_e, R_e, ω_e, B_e, α_e, the dipole moment µ_e, and the dissociation energy D_e have been calculated for the bound states. Moreover, the transition dipole moment curves (TDMCs) of the (X)¹Σ⁺-(1)¹Π, (X)¹Σ⁺-(2)¹Σ⁺ and (1)¹Π-(2)¹Σ⁺ transitions have been analyzed. A rovibrational study has been done to investigate the vibrational levels of the bound states and the vibrational constants E_v, B_v, D_v, R_min and R_max are calculated. These theoretical results are quite interesting for further experimental works, especially, in the advancement of creation of cold alkaline-earth monofluoride cations in the low-lying vibrational states.