Fourier Transform Observation of Jet Cooled Emission from the CH3N and CCN radicals

The gas phase spectrum of the methyl nitrene radical was first observed by Carrick and Engleking1and subsequently the first rotationally resolved spectrum was obtained by Carrick et al.2The use of the Kitt Peak Fourier transform spectrometer, to detect the emission from a corona excited supersonic expansion of methyl azaide in helium, yielded a rotationally resolved spectrum limited by Doppler broadening of 0.02 cm-1. The transition, assigned as A ˜ 3 E- X ˜ 3 A 2 analagous to the A3∏ −X3∑−band of NH, was still extremely complicated however. Due to the case (a) - case (b) nature of the transition 27 branches are allowed for each subband. Giving a total of 81 branches for the 0-1, 1-0 and 1-2 subbands, the only ones likely to be populated at 15 K the observed rotational temperature. Hence the observed transition is a many line spectrum with few branches discernable.