Structure and spectroscopic properties of the beryllium hydride ion BeH+: potential energy curves, spectroscopic constants, vibrational levels and permanent dipole moments

Ab initio calculations are performed for the beryllium hydride ion BeH+ dissociating into Be+(2s, 2p, 3s, 3p and 3d) + H (1s, 2s and 2p) and Be (2s(2), 2s2p, 2s3s, 2p(2), 2s3p and 2s3d)+ H+. We have used a standard quantum chemistry approach based on pseudopotential for atomic core representation Be2+, Gaussian basis sets, effective core polarization potentials, and full configuration interaction calculations. Potential energy curves and their spectroscopic constants for the ground state and the first 44 excited electronic states of (1,3)Sigma(+), (1,3)Pi and (1,3)Delta symmetries are determined. Their accuracy is discussed by comparing our well depths and equilibrium positions with the previous experimental and theoretical works. A very good agreement with the theoretical calculations and the few available experimental data is observed. Moreover, we localised and analysed numerous avoided crossings between the electronic states of (1,3)Sigma(+) and (1,3)Pi symmetries. Their existence are related to the interaction between electronic states and to the charge transfer process between the two ionic systems Be+H and BeH+. In addition, the vibrational energy level spacings are presented and compared with the available experimental and theoretical results. The permanent dipole moments for several electronic states of (1,3)Sigma(+), (1,3)Pi and (1,3)Delta symmetries are determined as function of the internuclear distance.