Quenching of Li ( 2 P) by H 2 : potential energy surfaces, conical intersection seam, and diabatic bases

Abstract

The quenching of Li (1s 22p; 2P) to Li (1s 22s; 2S) by H2 is considered using coupled-cluster and multireference configuration-interaction techniques. C 2 v (2A1, 2B2) and C ∞ v (2Π,2Σ+) sections of the 12A′ and 22A′ potential energy surfaces are determined. The C 2 v portion of the 12A′−22A′ seam of conical intersection is studied. Perhaps the most significant finding is a surprising trifurcation of this seam into a portion with only C s symmetry and the aforementioned C 2 v portion. The adiabatic-to-diabatic state transformation is considered in the vicinity of the seam of conical intersection using both perturbation theory and the dipole moment operator. The 2B2 section of the 22A′ potential energy surface exhibits an exciplex in the general vicinity of the seam of conical intersection. The 2Π section of the 22A′ potential energy surface possesses a global minimum lying 1.86kcal/mol below the Li (2P)+H2 asymptote. A van der Waals-like minimum with C ∞ v symmetry was found on the 12A′ potential energy surface.