Theoretical treatment of the X 1Σ+, A 1Σ+, and B 1Π states of LiH

Abstract

Ab initio self-consistent-field plus configuration-interaction calculations are reported for the X 1Σ+, A 1Σ +, and B 1Π states of LiH using a 22σ12π 7δ function Slater basis set. The resulting dissociation energies, with the experimental values in parentheses, are De (X 1Σ+)=19 972 (20 288) cm-1, D e(A 1Σ+)=9042 (8682) cm-1, and De (B 1Π)=284 (288) cm-1. This is the first ab initio treatment to quantitatively account for the binding in the B 1Π state. Calculated dipole moments and electronic transition moments for the X 1Σ+-A 1Σ +, X 1Σ+-B 1Π, and A 1Σ+-B 1Π band systems are in excellent agreement with existing theoretical and experimental data. Radiative transition probabilities and lifetimes, including both the bound→bound and bound→free contributions, are computed for all vibrational levels of the A 1Σ+ and B 1Π states. Comparison with previous results using experimentally based potentials provides insight into the sensitivity of the radiative lifetimes to the detailed nature of the uppermost region of the potentials. Our calculated lifetimes for the lower vibrational levels of the A 1Σ+ state are within the experimental uncertainty. Our calculated lifetimes for the three vibrational levels of the B 1Π state are in excellent agreement with those of Zemke and Stwalley (values in parentheses), increasing with υ′ from 11.3 (11.3) nsec at υ′=0, to 17.0 (17.0) nsec at υ′=1, and then to 23.5 (24.0) nsec at υ′=2. © 1981 American Institute of Physics.