Theoretical investigation of the low-lying electronic states of the alkaline hydride BeH2+ ion: Potential energy curves, spectroscopic constants, vibrational levels, and transition dipole functions

Abstract

The structure and spectroscopic properties of the alkaline hydride BeH2+ ion have been investigated using an ab initio approach based on nonempirical pseudopotentials and parameterized l-dependent polarization potentials. The adiabatic potential energy curves and their spectroscopic constants for the ground and seventeen excited electronic states, dissociating into Be+(2s, 2p, 3s, 3p, 3d, 4s, 4p, and 4d) + H+ and Be2+ + H(1s and n = 2), of 2Σ+, 2Π, and 2Δ symmetries have been determined. As no experimental data are available, our results are discussed and compared with the few existing theoretical calculations. A very good agreement has been found with the previous theoretical data for the ground state; however many potential energy curves for the higher excited states are presented here, for the first time. Numerous avoided crossings between electronic states for 2Σ+ and 2Π symmetries have been localized and analyzed. Their existence is related to the interaction between the electronic states and to the charge transfer process between the two ionic systems Be2+H and Be+H+. In addition, we have calculated the vibrational energy level spacings of the bound electronic states. Furthermore, the adiabatic transition dipole functions from the X2Σ+ and 22Σ+ states to the higher excited states of 2Σ+ and 2Π symmetries have been evaluated and compared with the available theoretical work. This study represents the necessary initial step towards the investigation of the charge transfer processes in collision between Be+-H+ and Be2+-H.