ROTATIONAL BANDSHAPES OF JET COOLED BENZYL RADICAL

$^{1}$ F. W. Birss, J. M. Brown, A. R. H. Cole, A. Lofthus, S. L. N. G. Krishnamachari, G. A. Osborne, J. Paldus, D. A. Ramsay, and L. Watmann, Can J. Phys., 48, 1230 (1970). $^{2}$ C. Cossart-Magos and S. Leach, J. Chem. Phys. 56 1534 (1972)Author Institution: Air Force Astronautics Laboratory/LSX; Department of Chemistry, University of RedlandsHigh resolution rotational emission spectra of the $1^{2} A_{2}\rightarrow 1^{2}B_{2}$ electronic ,$6b^{a}_{1}$ and $6a^{a}_{1}$ vibronic transitions of the benzyl radical were observed with the Fourier Transform Spectrometer at Kitt Peak National Observatory. The rotationally cooled, electronically excited benzyl radicals were produced from a mixture of toluene and helium passed through a corona excited supersonic expansion equipped with a slot nozzle. The resolved $6b^{0}_{1}$ bandshape was modeled using the asymmetric top modeling program developed by Birss $et al.^{1}$ The ground state rotational constants obtained from a fit of the resolved features of this band compare favorably well with those obtained from room temperature band contours measured by Cossart-Magos and $Leach.^{2}$ However the excited state constants obtained in this study are significantly different from the room temperature values. A rotational temperature of 20K was deduced by matching the intensities of the resolved branches with the calculated intensities. The $6a^{0}_{1}$ bandshape was also modeled with this same program and resulted in essentially the same rotational constants. However, the constants derived from this band are less certain due to reduced signal intensities