Selective production of photofragments by monitoring the shape of asymmetric resonances in OH photodissociation: Dependence on initial vibrational states

Abstract

Quantum mechanical analysis is presented on the vibrational state dependence of the total dissociation cross sections and the branching ratios of O(3Pj, j=0,1,2) in the predissociation of OH. Two transformation matrices, each of which describes the relation between an atomic term limit and the correlating molecular states, are constructed and incorporated in the close coupling calculations. The branching ratios of O(3Pj, j=0,1,2) depend very sensitively on the vibrational levels (v=0–4) of the initial X 2Π state. The variations of the spin–orbit distributions as a function of the excitation energy near the asymmetric resonances change markedly depending on the vibrational levels. The variations are either redshifted or blueshifted from the resonance position, depending on the degree of asymmetry of the resonances. The widths of the variations tend to increase with increasing vibrational quantum number of the initial state, suggesting the possibility of choosing the proper linewidths in the experiments to selectively produce the photofragments in one-photon process. Discussion is presented on the applicability of the theoretical scheme to analyze the recent measurements by Neumark and co-workers [J. Chem. Phys. 103, 2495 (1995)] on the product fine structure distributions in the predissociation of O2.