Adiabaticity of the nonreactive bond in atom-triatom reactions: a quantum mechanical study of the hydrogen atom + water .fwdarw. hydroxyl + hydrogen system

Abstract

This work is a quantum mechanical study of the four-atom process H + HzO - H2 + OH and its isotopic analogs. State-to-state reactive probabilities were calculated for the collinear configuration. The adiabaticity behavior with regard to the nhreactive bond, as established by Sinha et al. (J. Chem. Phys. 1991,94,4298), was confirmed for the H + HOD system but not for the H + H2O one. Enhancement of the reaction process due to vibrational excitation as was established by Sinha et al. and Bronikowski et al. (J. Chem. Phys. 1991, 95, 8645) was fully confirmed for the H + HOD system and for the H + HzO system. The calculations were carried out employing negative imaginary potentials to form absorbing boundary conditions. I. Iatroduction Confidence in the reliability of applying negative imaginary potentials (NIPS) to study time-independent scattering processes in general and exchange processes in particular has been steadily growing.l-l0 These potentials were applied not only t0collinear~9~9~ and other frozen configurations3 but to three-dimensional systems as ell.^.^ In case of the process D + Hz(uj) - HD (~7’) + H, state-testate reactive probabilities were calculated6 and the results compared with the results from more established approaches;’ very encouraging fits were obtained. Other groups have studied NIPS.~-~O In a detailed study, Seideman and Miller,lo confirmed that accurate reactive transition probabilities are well reproduced employing these potentials. These authors reported, moreover, that different types of potentials, e.g., the WoodsSaxon potential and/or power-law potentials, also yield accurate results, for a wide range of parameters. The present work extends these treatments to four-atom systems. We report on state-to-state reactive transition probabilities for the three isotopic reactions: