Vibronic emission spectrum of jet-cooled 3,4-difluorobenzyl radical generated in corona excited supersonic expansion

We applied the technique of corona excited supersonic expansion (CESE) to generate a vibronically excited but jet-cooled 3,4-difluorobenzyl radical from 3,4-difluorotoluene seeded in a large amount of inert carrier gas helium. The well-resolved vibronic emission spectrum of the radical, exhibiting an excellent S/N, was recorded in the visible region using a long path monochromator for the first time. From an analysis of the spectrum, we obtained the electronic energy of the D1 → D0 transition as well as the frequencies of the vibrational modes in the ground electronic state by comparison with those from an ab initio calculation.