Thermodynamic stability and spectroscopic properties of alkaline earth monobromides: The cases of MgBr2+ and BaBr2+

Abstract

The low-lying electronic states of the dications MgBr2+ and BaBr2+ are investigated at a high level of theory. Potential energy curves are constructed, and the associated spectroscopic parameters determined. BaBr2+ is thermodynamic stable and MgBr2+ metastable. The state X 2Π of BaBr2+ is bound (De) by 22.60 kcal mol−1, with (Re, ωe) equal to (6.146 a0, 123.9 cm−1). The state A 2Σ+ lies higher by 5049 cm−1 with De = 8.43 kcal mol−1, ωe = 86.9 cm−1. For the dication MgBr2+, the state X 2Π has a deep well with an effective De (barrier height) of 51.18 kcal mol−1, Re = 4.500 a0, and ωe = 308.3 cm−1. The first excited state (A 2Σ+) lies higher by 12,091 cm−1 with De = 26.48 kcal mol−1, ωe = 236.6 cm−1. Einstein spontaneous emission coefficients (Av́v́́) are reported, and lifetimes estimated. New experimental results for the mass spectra of MgBr2+ are also provided.