Nonadiabatic effects in photodissociation dynamics: A quantum mechanical study of ICN photodissociation in the A continuum

The photodissociation dynamics of ICN in the A continuum has been studied using a quantum coupled-channel method. The two-state empirical potential energy surfaces derived by Goldfield et al. are used in our calculations, and the CN bond is assumed frozen throughout the dissociation (rigid-rotor approximation). The excited state dynamics involving nonadiabatic transitions between the I and I* channels is treated in a diabatic representation. The CN rotational distributions have been obtained for several wavelengths and zero total angular momentum by calculating the appropriate Franck–Condon integral. Bimodal structure in CN rotational distributions is obtained in the quantum calculations, but the width of the peaks is narrower than in semiclassical results for the same surfaces. Discrepancies between quantum and semiclassical results are also found in the total cross-section and in the I*/I branching ratio. Comparison of our quantum results with experiment indicates that the potentials derived from the semi-classical calculations are not accurate enough to describe the ICN photodissociation dynamics. Further modifications are needed for the potential energy surfaces.