Ultrafast Photodissociation Dynamics of Highly Excited Iodobenzene on the C Band

The photodissociation dynamics of highly excited iodobenzene from the C band absorption has been studied by femtosecond time-resolved ion yields techniques. Detailed photodissociation routes are discussed with the aid of high-level, spin–orbit resolved ab initio calculations of 1D potential energy curves. Upon 200 nm excitation within the C band, iodobenzene molecules on 7B2 and 7B1 states decay to 7A1 and 8B2 states through internal conversion in 75 fs, with electronic energy converted into high vibrational energy of 7A1 and 8B2 states. Subsequently, 7A1 and 8B2 states decay through internal vibrational energy redistribution in 540 fs, accompanied by the excited C–I mode and the resulting cleavage of the C–I bond. The overall time for the reaction starting from the phenyl-type modes and ending in final C–I fragmentation for I(2P3/2) production is 1.2 ps.