Ab initio configuration interaction study of the low-lying [sup 1] Sigma[sup +] electronic states of LiCl

Ab initio configuration interaction calculations have been performed for the X 1Σ+ and B 1Σ+ electronic states of LiCl. Potential energy curves, dipole moment functions, and dipole transition moments have been computed for internuclear distances between R = 2.5a0 and 50a0. Single- and double-excitation configuration interaction wave functions were constructed using molecular orbitals obtained from a two-state averaged multiconfiguration self-consistent-field calculation. This procedure yielded an accurate energy splitting between the covalent and ionic separated-atom limits. The calculated avoided crossing of the X and B state curves occurs at R = 16.2a0, in close agreement with previous calculations using a semiempirical covalent–ionic resonance model. X 1Σ+ state spectroscopic constants are in excellent agreement with experimental values.© 2004 American Institute of Physics.