Quantum dynamics of Renner–Teller vibronic coupling: The predissociation of HCO

Abstract

A Hamiltonian model and parity-adapted wave packet representation are developed to describe a rotating triatomic system with two Renner–Teller coupled potential surfaces, and HCO predissociation is studied. New configuration interaction calculations on HCO are performed to determine its excited Ã(2A″) potential surface, and Bowman, Bittman, and Harding’s X̃(2A′) ground potential surface is employed. The properties of many resonances, correlating with stretch/bend excitations on the A″ surface, are determined. Resonance energies and decay constants are in good agreement with experimental results of Houston and co-workers, but CO rotational product distributions tend to be hotter and narrower than experiment, particularly for pure bend excitations. Wave packet dynamics involves growth of amplitude on the A′ surface near collinear geometries via Renner–Teller coupling, and subsequent adiabatic evolution to determine product distributions. The wave packets probe a previously untested part of the A′ surface, and point to the need for improvements of this surface.