A new predissociated 2Σ+ state of the BeCl molecule

Abstract

Ten bands belonging to a new B2Σ+–X2Σ+ system of the BeCl molecule have been discovered in emission between 1990 and 2175 Å. The bands of both isotopes Be35Cl and Be37Cl have been photographed at high resolution and the most intense ones have been rotationally analyzed. Only three levels of the excited state have been observed and they present vibrational and rotational perturbations. The principal molecular constants of the new B2Σ+ state of Be35Cl are: v00 = 48 827.6, ΔG1/2 = 925.5, ΔG3/2 = 1212.7, Be = 0.7751, De = 3.5 × 10−6 cm−1, and the equilibrium internuclear distance is 1.7422 Å. The unusual intensity distribution in the bands can be tentatively interpreted as the result of an inverse predissociation which leads to a value of D″0 = 27 800 ± 500 cm−1 (3.45 ± 0.06 eV) for the dissociation energy of the ground state of the BeCl molecule. This value is at variance with thermochemical data.