Research of valence character HCl− states through nearly diabatic CI calculations

A b initio CI calculations have been performed for the HCl− system, using moderately large basis sets. For large interactomic distances, the potential curves of the three bound states (two 2∑+ and one 2Π) compare favorably with those previously computed with very large basis sets. The extension of a recently published procedure yields nearly diabatic potential curves for the unbound region, and enables to discriminate between valence-like resonant states, of essentially repulsive character and diffuse states, the potential curves of which parallel one of the neutral molecule curves; the former are nearly basis-set independent while the latter are sensitive to the basis. Estimations of the widths are also given. For the HCl equilibrium distance, the first 2∑+ ‘‘resonant state’’ is located at 2.3 eV above the v=0 level of HCl, with a large width of 2 eV; the second 2∑+ and 2Π resonant states are located at 9.4 and 7.1 eV, respectively, with widths of 2.5 and 1.2 eV.