Infrared fluorescence from multiphoton dissociation of vinyl bromide: Emission from the products and the parent molecule

A time-resolved study of the infrared fluorescence emission produced in the infrared multiphoton dissociation of vinyl bromide at different experimental conditions has been carried out. Two different regimes, namely unimolecular and collisional, have been identified and characterized through the parent vinyl bromide and the HBr and C2H2 photoproducts emissions. In the pressure interval studied, the formation of HBr has been determined to be mainly unimolecular, while the C2H2 is produced through a collisionally assisted photodecomposition process. The collisional regime is explained in terms of the 3-centre elimination channel while the unimolecular regime is ascribed to the 4-centre mechanism. Relaxation rate constants for both the vibrationally excited HBr by vinyl bromide and by Ar and for vibrational excited VBr by unexcited VBr, are reported.