title: Signatures of non-adiabatic dynamics in the fine-structure state distributions of the OH(X̃/Ã) products in the B-band photodissociation of H2O.
abstract: A detailed quantum mechanical characterization of the photodissociation dynamics of H2O at 121.6 nm is presented. The calculations were performed using a full-dimensional wave packet method on coupled potential energy surfaces of all relevant electronic states. Our state-to-state model permits a detailed analysis of the OH(X̃/Ã) product fine-structure populations as a probe of the non-adiabatic dissociation dynamics. The calculated rotational state distributions of the two Λ-doublet levels of OH(X̃, v = 0) exhibit very different characteristics. The A' states, produced mostly via the B̃→X̃ conical intersection pathway, have significantly higher populations than the A″ counterparts, which are primarily from the B̃→Ã Renner-Teller pathway. The former features a highly inverted and oscillatory rotational state distribution, while the latter has a smooth distribution with much less rotational excitation. In good agreement with experiment, the calculated total OH(X̃) rotational state distribution and anisotropy parameters show clear even-odd oscillations, which can be attributed to a quantum mechanical interference between waves emanating from the HOH and HHO conical intersections in the B̃→X̃ non-adiabatic pathway. On the other hand, the experiment-theory agreement for the OH(Ã) fragment is also satisfactory, although some small quantitative differences suggest remaining imperfections of the ab initio based potential energy surfaces.
authors.affiliation: Key Laboratory of Mesoscopic Chemistry, School of Chemistry and Chemical Engineering, Institute of Theoretical and Computational Chemistry, Nanjing University, Nanjing 210093, China.
authors.forename: Linsen
authors.initials: L
authors.lastname: Zhou
authors.affiliation: Key Laboratory of Mesoscopic Chemistry, School of Chemistry and Chemical Engineering, Institute of Theoretical and Computational Chemistry, Nanjing University, Nanjing 210093, China.
authors.forename: Daiqian
authors.initials: D
authors.lastname: Xie
authors.affiliation: Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131, USA.
authors.forename: Hua
authors.initials: H
authors.lastname: Guo