NO(X 2Π) rotational distributions from the photodissociation of NOCl and NOBr at 450 and 470 nm

Abstract

The rotational, Λ doublet and spin state distributions of the NO fragment following dissociation from NOCl and NOBr have been measured using a one-colour photolysis analysis laser scheme. Dissociation was by one photon at 450 or 470 nm while two-photonnon-resonant LIF at the same wavelength was used to probe the NO fragment. The NO rotational distributions for both precursors are found to be inverted and non-Boltzmann with states up to N=60 populated. Similar Λ doublet ratios of 1.7 and 1.6 for NOCl and NOBr respectively are observed. A statistical F2/F1 spin state population has been measured for NO from NOBr photolysis, however, the spin ratio from NOCl is found to be non-statistical with F2/F1 = 2.1. Sub-Doppler nascent NO line profiles reveal Cl is formed principally in the lower P32 state but Br in either P12 or P32 depending on the vibrational and rotational state of the NO fragment. In addition, the line profiles demonstrate a predictable perpendicular v-j correlation corresponding to planar dissociation and also allow the assignment of the accessed electronic transitions. Coupled with alignment measurements, A0(2) and βeff, the excited state symmetries are assigned.