Resonance rotational Raman scattering of symmetric tops: A probe of molecular photodissociation

Abstract

Expressions are derived using irreducible tensor notation describing resonance rotational Raman scattering intensities for symmetric top molecules. Isotropic, antisymmetric, and anisotropic scattering contributions to the resonance O, P, Q, R, and S rotational Raman transitions are considered. Excited state lifetimes in the range of ∼0.02 to 1 ps or ∼1 to 100 vibrational periods can be determined by fitting the pattern of observed relative ΔJ=0 and ΔJ≠0 rotational or rovibrational scattering intensities. UV Raman scattering spectra resonant with photodissociative levels of the X̃→Ã Rydberg transition of NH3 and ND3 are used to illustrate this technique. Rates of ammonia photodissociation are found to have a strong dependence on the excited bending level quantum number.