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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.

We observed, for the first time, the vibronic emission spectrum of the jet-cooled mesityl radical that was formed from mesitylene seeded in a large amount of inert carrier gas helium using a pinhole-type glass nozzle in a corona excited supersonic expansion. The well-resolved vibronic emission spectrum was recorded in the visible region with a long path monochromator. The spectrum was analyzed to identify the origin of the D(2) --> D(0) and D(1) --> D(0) transitions as well as the frequencies of the vibrational modes in the ground electronic state of the mesityl radical by comparison with those of the known data of the precursor and an ab initio calculation.

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We report the first spectroscopic evidence of the o-chloro-alpha-methylbenzyl radical. The electronically hot but jet-cooled o-chloro-alpha-methylbenzyl radical was formed from precursor o-chloro-ethylbenzene seeded in a large amount of inert carrier gas helium, by employing the technique of corona excited supersonic expansion with a pinhole-type glass nozzle. The vibronic emission spectrum was recorded with a long path monochromator in the D(1) --> D(0) electronic transition in the visible region. By comparing the observed spectrum with that of the o-chlorobenzyl radical reported previously, we could easily identify the spectroscopic evidence of the jet-cooled o-chloro-alpha-methylbenzyl radical generated in the corona discharge of o-chloro-ethylbenzene, from which the electronic transition energy and several vibrational mode frequencies in the ground electronic state were accurately determined.