OBSERVATION OF ROTATIONAL COOLING OF CN(B2-SIGMA+) RADICAL GENERATED IN A SUPERSONIC EXPANSION

The CN(B2SIGMA+) radical was produced in a jet using an electric dc discharge of the precursor CH3CN with inert carrier gases. The rotationally resolved Fourier transform emission spectra of the 0-0 band of the B2SIGMA+-->X2SIGMA+ transition of CN have exhibited different distribution of the intensity for the carrier gases He and Ar, respectively. From the analysis of intensity distribution in the spectra, the mechanism for rotational cooling process of CN radical in a supersonic expansion has been suggested.