Spectroscopic evidence of jet-cooled p-methyl-α-methylbenzyl radical

Abstract We report spectroscopic evidence of the jet-cooled p -methyl-α-methylbenzyl radical in corona discharge. The visible vibronic emission spectra were recorded from the corona discharge of three precursors, p -xylene, p -ethyltoluene, and p -isopropyltoluene seeded in a large amount of carrier gas helium using a pinhole-type glass nozzle. From the analysis of the vibronic spectra observed from each precursor and the bond dissociation energies of precursor molecules, we are able to confirm the formation of the jet-cooled p -methyl-α-methylbenzyl radical in corona discharge, and determine the energy of the D 1  → D 0 transition and a few vibrational mode frequencies in the D 0 state.