Nonadiabatic Electronic Interactions In The Ion-Pair States Of NelCl

Nonadiabatic interactions in the NeICI van der Waals complex have been explored in the lowest energy triad ofICI ion-pair states (~39 000 cm-I). Dispersed fluorescence measurements reveal emission characteristic of multiple ion-pair electronic states, with the relative contributions from the E(0 +), P(1), and D I (2) states changing with the initial ICI vibrational excitation (VICI)' Emission directly from NelCI (V IC1 = 0) complexes indicates that the initially prepared NelCI levels have mixed electronic character and that the ICI electronic parentage changes with the initial van der Waals vibrational level selected. NelCI complexes prepared with 1-4 quanta of ICI stretch undergo rapid vibrational predissociation with a strong propensity for £lV 1C1 =-1 relaxation. The electronic state(s) populated in the ICI fragments differ from the mixed electronic character of the initially prepared level, demonstrating that vibrational predissociation is accompanied by nonadiabatic electronic state changing processes. The observed final state selectivity may be attributed to the relative strength of the nonadiabatic couplings between the initial NelCI bound state and the final ICI states or a momentum gap rationale based on the overlap between the NelCI bound state wave function and the highly oscillatory continuum wave function of the separating fragments.