Laser-induced fluorescence of the trans-CHBrCHO radical

A new laser-induced fluorescence spectrum was observed in the region of 350 nm-360 nm. The spectrum was observed in the reaction between the CHBrCHBr and OH radicals and in the reaction of CHBrCHBr and CH₂CHBr with atomic oxygen O(³P). The spectrum was assigned to the B̃--X̃ transition of the trans-CHBrCHO (trans-2-bromovinoxy) radical. The B̃--X̃ electronic transition energy (T₀) was 28 542 cm^-1, which was 242 cm^-1 lower than that of the unsubstituted vinoxy radical (CH₂CHO). From an analysis of the laser-induced single vibronic level fluorescence aided by ab initio calculations, some of the vibrational frequencies were assigned to the ground electronic state ν₃ (C-O str.) = 1581 cm^-1, ν₆ (C-C str.) = 1130 cm^-1, and ν₈ (C-C-O bend.) = 409 cm^-1. The fluorescence lifetimes of the excited B̃ state were 35 ns-75 ns, depending on the excited vibrational modes, implying that predissociation had accelerated as the energy level (v') increased.