A high-resolution study of the NO3 radical produced in a supersonic jet

The 0(0)(0) vibrational band of the (B) over tilde (2)E' <-- (X) over tilde (2)A'(2) transition in the jet-cooled NO3 radical has been studied at high resolution in the frequency- and time-domains. Under these cold conditions, the absorption band exhibits vibrational and rotational structure. The fluorescence decays are consistent with the previously reported fluorescence lifetime and some show superimposed quantum beats. A two-tier coupling scheme is proposed: the (B) over tilde (2)E' upsilon = 0 level is vibronically coupled to vibrational levels in the (A) over tilde and/or (X) over tilde state, which are in turn coupled to ground state levels. Estimates of the pertinent coupling matrix elements and state densities are given.