HCL(B1∑+) and HBr(B1∑+) Emission From the Ultraviolet Multiphoton Dissociation of Vinyl Chloride and Bromide

Multiphoton dissociation processes of vinyl chloride and bromide were studied with a broadband ArFlaser at 193 nm and with a narrowband tunable laser in the region of 212 nm, in the peak and in thethreshold of the absorption band, respectively, for both compounds. Photolysis at 193 nm gives rise tothe corresponding hydrogen halide in the B 1 ∑ + excited state which results in an intense UV emission. However these emissions are absent when photodissociation was performed with the narrow band dyelaser around 212 nm. These results, together with a calculation of the observed spectra, give furthersupport to a mechanism which invokes one-photon resonant absorption of vibrationally hot ground statehydrogen halide as the process which populates the excited B 1 ∑ + state of the fragment.