Doppler-resolved spectroscopy as an assignment tool in the spectrum of singlet methylene

New spectra of methylene, CH2, in the near-infrared are obtained following 308 nm photolysis of ketene, CH2CO. Nascent photofragment Doppler spectra and thermalization kinetics vary systematically with the energy of the absorbing level, providing additional information to support or refute spectroscopic assignments made on the basis of the frequency measurements and combination differences.