Cavity ring-down spectroscopy of the phenyl radical in a pulsed discharge supersonic jet expansion

Absorption spectra for the 1 2 B 1 - X ˜ 2 A 1 transition of the phenyl radical have been recorded using the technique of cavity ring-down spectroscopy. The radicals were produced by an electric discharge through Ar/C6H5Br mixtures and cooled by supersonic expansion. Partially resolved rotational structure was observed for the 0 0 0 , 9 0 1 , and 10 0 1 bands, and excited state rotational constants were derived from these data. For the 9 0 1 band, homogeneous line broadening was indicative of an excited state lifetime of 96 ps.