Theoretical study of the dipole moment function of the A 1Σ+ state of LiH

Abstract

A theoretical study of the A ¹Σ^{+ 7}LiH dipole moment function is reported. A new theoretical A ¹Σ⁺ potential energy curve, obtained by accounting for essentially all of the electron correlation within a large flexible Slater basis set, is reported here for the first time. The calculated equilibrium geometry (R_e) and dissociation energy (D_e) of this new potential are in close agreement with experimental values (given in parentheses): 4.825 (4.883) bohr and 8653 (8682) cm⁻¹, respectively. The vibrational spacings (ΔG_v+(1/2)) for all levels (0⩽v⩽26) are also in agreement with experiment. The dipole moment function derived from this potential, as well as the previous theoretical dipole moment functions of Partridge and Langhoff and of Docken and Hinze, are used to obtain vibrationally averaged dipole moments μ_v for all of the vibrational levels of the A ¹Σ⁺ state of ⁷LiH. Of particular interest is μ₅, the dipole moment for the v = 5 level, measured recently by two separate experimental methods. Experimentally, the sign of μ₅ is uncertain, but these theoretical results strongly suggest that μ₅ is negative (i.e., Li⁻H⁺).