title: Photodissociation of bromobenzene, dibromobenzene, and 1,3,5-tribromobenzene.
abstract: Quantum chemical calculations have been performed on the ground state and several low-lying excited states of bromobenzene, ortho-, meta-, and para-dibromobenzene, and 1,3,5-tribromobenzene using high-level ab initio and hybrid density-functional methods. Experimental observations of ultrafast predissociation in these molecules are clarified from extensive theoretical information about all low-energy potential-energy curves together with symmetry arguments. The intriguing observation that o- and m-dibromobenzene have two ultrafast predissociation channels while bromobenzene, p-dibromobenzene, and 1,3,5-tribromobenzene only have one such channel is explained from the calculated potential-energy curves. These show that the lowering of point-group symmetry from C2v to Cs along the main photodissociation reaction coordinate, which only occurs in o- and m-dibromobenzene, opens up a new predissociation channel. Dynamical quantum simulations based on the calculated potential-energy curves are used to estimate the coupling strength at the intersystem crossing point in bromobenzene.
authors.affiliation: Department of Quantum Chemistry, Uppsala University, Box 518, 751 20 Uppsala, Sweden.
authors.forename: Ya-Jun
authors.initials: YJ
authors.lastname: Liu
authors.forename: Petter
authors.initials: P
authors.lastname: Persson
authors.forename: Hans O
authors.initials: HO
authors.lastname: Karlsson
authors.forename: Sten
authors.initials: S
authors.lastname: Lunell
authors.forename: Malin
authors.initials: M
authors.lastname: Kadi
authors.forename: Daniel
authors.initials: D
authors.lastname: Karlsson
authors.forename: Jan
authors.initials: J
authors.lastname: Davidsson