A THEORETICAL ANALYSIS OF THE DISSOCIATION OF OH RADICAL: FINE-STRUCTURE DISTRIBUTIONS OF THE O(3PJ) PRODUCT

Abstract

A theoretical treatment is presented for the nonadiabatic photodissociation of hydroxyl radical. Five electronic states, X 2Π, A 2Σ+, 14Σ-, 12Σ- and 14Π, are included in this simulation. Based on the accurate ab initio calculations of the potential energy curves, transition dipole moments and nonadiabatic couplings between the relevant states, the dissociation dynamics are investigated using the time-dependent quantum wave packet approach. The direct dissociation, following the excitation from the specific vibrational levels of the ground state X 2Π to the repulsive state 12Σ- is examined, where the total and partial cross sections and the branching fractions of spin–orbit fine-structures of O (3 P J) are calculated over a wide range of the incident photon frequencies. For the predissociation via the bound excited state A 2Σ+, the influence of the nonadiabatic interactions in different internuclear regions and the role of the repulsive states in the dissociation starting at different vibrational levels are also analyzed through the spin–orbit branching fractions of products.