MRSDCI study on potential energy curves and ro-vibrational spectra of the BBr molecule

Abstract

Four low-lying electronic states of the BBr molecule, including Σ+ symmetry and Π symmetry with singlet and triplet spin multiplicities, have been studied using the complete active space self-consistent-field method followed by multi-reference single and double excitation configuration interaction calculation. For the ground state, four isotopes (11B79Br, 11B81, 10B79Br, 10B81Br) of the BBr molecule have been studied, since their experimental spectroscopic constants and ro-vibrational energy levels are abundant. For the three excited states, just the most natural abundance isotope–11B79Br–is investigated. The spin–orbital coupling effect for the a3Π state is also considered. Finally, the analytical potential energy functions of these states are fitted except for the 3Σ+ state because its potential well is too shallow to be fitted with available functions. These results have been compared in detail with those of the investigations reported in the literature.