Doppler-resolved Spectroscopy Research Articles

Doppler-Resolved Spectroscopy as an Assignment Tool in the Spectrum of Singlet Methylene

New spectra of methylene, CH2, in the near-infrared have been 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. New assignments in the 10800 cm-1 region extend to higher rotational levels than before and provide new spectroscopic term values for some CH2 ã1A1 state levels. The number and intensity distribution of unassigned lines in the spectrum is consistent with the expected transitions from vibrationally excited and high rotational levels of the ã1A1 state and transitions due to 13CH2 in natural abundance, and does not require a significant contribution from additional transitions arising from triplet-state perturbations.