Photodissociation of water. II. Wave packet calculations for the photofragmentation of H2O and D2O in the (B)over-tilde band

A complete three-dimensional quantum mechanical description of the photodis sociation of water in the B-over-tilde band, starting from its rotational g round state, is presented. In order to include B-over-tilde-X-over-tilde vi bronic coupling and the B-over-tilde-A-over-tilde Renner-Teller coupling, d iabatic electronic states have been constructed from adiabatic electronic s tates and matrix elements of the electronic angular momentum operators, fol lowing the procedure developed by A. J. Dobbyn and P. J. Knowles [Mol. Phys . 91, 1107 (1997)], using the ab initio results discussed in the preceding paper. The dynamics is studied using wave packet methods, and the evolution of the time-dependent wave function is discussed in detail. Results for th e H2O and D2O absorption spectra, OH(A)/OH(X) and OD(A)/OD(X) branching rat ios, and rovibrational distributions of the OH and OD fragments are present ed and compared with available experimental data. The present theoretical r esults agree at least qualitatively with the experiments. The calculations show that the absorption spectrum and the product state distributions are s trongly influenced by long-lived resonances on the adiabatic B-over-tilde s tate. It is also shown that molecular rotation plays an important role in t he photofragmentation process, due to both the Renner-Teller B-over-tilde-X -over-tilde mixing, and the strong effect of out-of-plane molecular rotatio ns (K > 0) on the dynamics at near linear HOH and HHO geometries. (C) 2000 American Institute of Physics. [S0021-9606(00)31013-3].