Mapping of transition-state wave functions: I. Rotational state distributions following the decay of long-lived resonances in the photodissociation of HONO(S1)

Abstract

We investigate final rotational state distributions following the decay of long-lived resonance states with k*=0, 1, and 2 quanta of internal bending excitation. The calculations are related to the photodissociation of HONO on the S1 electronic state surface, truncated to two degrees of freedom namely the HO–NO dissociation bond and the ONO bending angle. The decay of the k*=0 resonance yields a smooth Gaussian-type distribution, in very good agreement with recent measurements. The distributions following the decay of the excited bending states show a bimodal behavior with the main maxima at high rotational states. The final angular momentum distributions reflect the coordinate-dependence of the dissociation wave function in the region of the transition state, mediated by the dynamics in the exit channel when the wave packet slides down the steep potential slope. A qualitative interpretation of the rotational state distributions is provided by a simple classical model which applies the transition-state wave function as a weighting for trajectories starting on a line that separates the intermediate complex from the product channel.