Spectroscopic identification of isomeric jet-cooled benzyl-type radicals generated from 4-fluoro-o-xylene.

Vibronically excited but jet-cooled benzyl-type radicals were generated by the corona discharge of precursor 4-fluoro-o-xylene seeded in a large amount of inert carrier gas helium using a pinhole-type glass nozzle, from which the vibronic emission spectra were observed with a long-path monochromator in the visible region. From an analysis of the spectra observed, we identified the existence of two isomeric benzyl-type radicals, 2-methyl-4-fluorobenzyl and 2-methyl-5-fluorobenzyl radicals in corona discharge, and determined the electronic energy of the D1 → D0 transition and several vibrational mode frequencies in the D0 state of both isomers for the first time.