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

Abstract

Multiphoton dissociation processes of vinyl chloride and bromide were studied with a broadband ArF laser at 193 nm and with a narrowband tunable laser in the region of 212 nm, in the peak and in the threshold of the absorption band, respectively, for both compounds. Photolysis at 193 nm gives rise to the corresponding hydrogen halide in the B¹∑⁺ excited state which results in an intense UV emission. However these emissions are absent when photodissociation was performed with the narrow band dye laser around 212 nm. These results, together with a calculation of the observed spectra, give further support to a mechanism which invokes one-photon resonant absorption of vibrationally hot ground state hydrogen halide as the process which populates the excited B¹∑⁺ state of the fragment.