Observation of vibronic emission spectrum of jet-cooled duryl radical in corona excitation.

The vibronically excited but jet-cooled 2,4,5-trimethylbenzyl (duryl) radical was formed in a corona excitation from precursor 1,2,4,5-tetramethylbenzene (durene) seeded in a large amount of inert carrier gas helium using a pinhole-type glass nozzle. The vibronically resolved emission spectrum of the jet-cooled duryl radical was recorded, for the first time, with a long path monochromator in the visible region. The spectrum was analyzed to obtain an accurate electronic energy of the D1-->D0 transition and vibrational mode frequencies in the ground electronic state by comparing with those of the precursor and those from an ab initio calculation.