MRCI study on the spectroscopic parameters, transition dipole moments and transition probabilities of 16 low-lying states of the BeB radical

In this work, we calculate the potential energy curves of 16 Lambda-S and 36 Omega states of beryllium boride (BeB) radical using the complete active space self-consistent field method, followed by the valence internally contracted multireference configuration interaction approach with Davidson correction. The 16 Lambda-S states are the X-2 Pi, A(2)Sigma(+), B-2 Pi, C-2 Delta, D-2 Sigma(-), E-2 Sigma(+), G(2)Pi, I-2 Sigma(+), a(4)Sigma(-), b(4)Pi, c(4)Sigma(-), d(4)Delta, e(4)Sigma(+), g4(Pi), h(4)Pi, and 2(4)Sigma(+), which are obtained from the first three dissociation channels of the BeB radical. The Omega states are obtained from the A-S states. Of the Lambda-S states, the G(2)Pi, I-2 Sigma(+), and h(4)Pi states exhibit double well curves. The G(2)Pi, b(4)Pi, and G(4)Pi states are inverted with the spin-orbit coupling effect included. The d(4)Delta, e(4)Sigma(+), and ell states as well as the second well of the h(4)Pi state are very weakly bound. Avoided crossings exist between the G(2)Pi and h(2)Pi states, the A(2)Sigma(+) and Sigma(2)Sigma(+) states, the c(4)Sigma(-) and f(4)Sigma(-) states, the g(4)Pi and h(4)Pi states, the I-2 Sigma(+) and 4(2)Sigma(+) states, as well as the 2(4)Sigma(+) and 3(4)Sigma(+) states. To improve the quality of the potential energy curves, core-valence correlation and scalar relativistic corrections, as well as the extrapolation of the potential energies to the complete basis set limit, are included. The transition dipole moments are computed. Spectroscopic parameters and vibrational levels are determined along with Franck-Condon factors, Einstein coefficients, and radiative lifetimes of many electronic transitions. The transition probabilities are evaluated. The spin-orbit coupling effect on the spectroscopic parameters and vibrational levels is discussed. The spectroscopic parameters, vibrational levels, and transition probabilities reported in this paper can be considered very reliable and can be employed to predict these states in an appropriate spectroscopy experiment. (C) 2018 Elsevier Ltd. All rights reserved.