JET COOLED EMISSION SPECTRA OF THE XYLYL RADICALS

Abstract

Jet cooled electronic emission spectra from ortho, meta, and para-xylyl (methylbenzyl) radicals have been recorded using a corona excited supersonic expansion (CESE) apparatus. A full vibronic analysis of the $D_{1} \rightarrow D_{0}$ transitions for all three isomers has been carried out allowing for unambiguous assignments of the gas phase ground state vibrational frequencies. Based on band contours observed for the para-xylyl radical, the band at $458.3 cm^{-1}$ is reassigned to the 6b vibration instead of the 6a vibration. For the vibrational modes exhibiting progressions, anharmonicity constants are calculated. Temperatures of approximately 15 K were attained. Although CESE excitation of the xylenes (used in this study as precursors) did not result in the interconversion of isomers, it does occur along with homolytic methyl C-H bond dissociation during the formation of the radicals.