Spectroscopic investigations on HBr(X1Σ+) molecule using MRCI method in combination with correlation-consistent quintuple basis set augmented with diffuse functions

The equilibrium internuclear separation, harmonic frequency, dissociation energy and potential energy curve (PEC) of the HBr(X1Σ+) molecule have been investigated by using the highly accurate valence internally contracted multireference configuration interaction (MRCI) approach in combination with the correlation-consistent quintuple basis set augmented with diffuse functions, aug-cc-pV5Z, in the valence range. The PEC calculations cover the internuclear distance range from 0.08 to 2.08 nm. The PEC is fitted to the analytic Murrell-Sorbie function, which is used to reproduce the spectroscopic parameters, such as ωeχe, αe, Be and D0. The present D0, De, Re, ωe, ωeχe, αe and Be are of 3.7665 eV, 3.9289 eV, 0.14195 nm, 2642.68 cm−1, 45.6118 cm−1, 0.23525 cm−1 and 8.40417 cm−1, respectively, which almost perfectly conform to the available measurements. With the potential determined at the MRCI/aug-cc-pV5Z level of theory, the total of 20 vibrational states is predicted when the rotational quantum number J is set to equal zero (J = 0) by numerically solving the radial Schrödinger equation of nuclear motion. The complete vibrational levels, classical turning points, inertial rotation and centrifugal distortion constants are determined when J = 0 for the first time, which are in excellent agreement with the available experimental data.