High-level ab initio study of LiO (X 2Π;A 2Σ+) and [formula omitted]: the ionization energy of LiO

Abstract

RCCSD(T) calculations are performed using basis sets of quadruple- and quintuple-ζ quality. Potential energy curves are calculated for the lowest two neutral states of LiO (X 2 Π and A 2 Σ +), as well as the lowest two triplet states of LiO + (X 3 Σ − and A 3 Π). From these curves spectroscopic parameters are calculated, including anharmonic vibrational frequencies and rotational constants. For the X 2 Π state, excellent agreement with microwave and infrared values is obtained. The 2Σ +– 2Π separation is calculated to be 2419 cm −1 , and the first adiabatic ionization energy (AIE) corresponding to the process X 3 Σ −←X 2 Π is calculated to be 8.55±0.05 eV .