PHOTODISSOCIATION STUDIES ON NITROSYL BROMIDE - I - PHOTOFRAGMENT SPECTROSCOPY AND ELECTRONIC-STRUCTURE

The UV-visible absorption spectrum of nitrosyl bromide (BrNO) was reco rded. The spectrum exhibits several broad features in the 200-730 nm r egion. To aid the assignment of the spectrum, photodissociation experi ments were carried out at several selected excitation wavelengths. Res onance-enhanced multiphoton-ionization spectra of both the NO and Br f ragments as well as photofragment time-of-flight profiles were recorde d. The electronic transitions were assigned based on the observed spat ial anisotropy parameters (beta), the Br spin orbit state population, and NO rotational, vibrational, spin-orbit, Lambda-doublet state popul ations, as well as comparisons with isovalent ClNO system. The stronge st UV band peaked around 210 Mm was attributed to the parallel S-5 <-- S-0 transition (sigma(Br-N)<--sigma(Br-N)) while all other features a t longer wavelengths were assigned to transitions to excited triplet s tates. The intensity borrowing from the S-5 State is responsible for t he apparent parallel nature of these singlet-triplet transitions. Impl ications of this assignment on the electronic structure and the non-ad iabatic dissociation dynamics are discussed. (C) 1998 American Institu te of Physics.