title: Spin-orbit ab initio investigation of the ultraviolet photolysis of diiodomethane.
abstract: The UV photodissociation (<5 eV) of diiodomethane (CH(2)I(2)) is investigated by spin-orbit ab initio calculations. The experimentally observed photodissociation channels in the gas and condensed phases are clearly assigned by multi-state second-order multiconfigurational perturbation theory in conjunction with spin-orbit interaction through complete active space-state interaction potential energy curves. The calculated results indicate that the fast dissociations of the first two singlet states of CH(2)I(2) and CH(2)I--I lead to geminate-radical products, CH(2)I (.)+I((2)P(3/2)) or CH(2)I (.)+ I*((2)P(1/2)). The recombination process from CH(2)I--I to CH(2)I(2) is explained by an isomerization process and a secondary photodissociation reaction of CH(2)I--I. Finally, the study reveals that spin-orbits effects are significant in the quantitative analysis of the electronic spectrum of the CH(2)I--I species.
authors.affiliation: College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China. yajun.liu@bnu.edu.cn
authors.forename: Ya-Jun
authors.initials: YJ
authors.lastname: Liu
authors.forename: Luca
authors.initials: L
authors.lastname: De Vico
authors.forename: Roland
authors.initials: R
authors.lastname: Lindh
authors.forename: Wei-Hai
authors.initials: WH
authors.lastname: Fang