Photodissociation of bromobenzene, dibromobenzene, and 1,3,5-tribromobenzene.
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.
Liu
Ya-Jun
YJ
Department of Quantum Chemistry, Uppsala University, Box 518, 751 20 Uppsala, Sweden.
Persson
Petter
P
Karlsson
Hans O
HO
Lunell
Sten
S
Kadi
Malin
M
Karlsson
Daniel
D
Davidsson
Jan
J