SPECTROSCOPIC IDENTIFICATION OF NEW BENZYL-TYPE RADICALS IN CORONA EXCITATION: CHLORO-$\alpha$-METHYLBENZYL RADICALS

Abstract

Using a pinhole-type glass nozzle coupled with corona excited supersonic expansion (CESE), precursors $o$- and $p$-chloro-ethylbenzenes seeded in a large amount of inert carrier gas helium were corona discharged to produce jet-cooled benzyl-type radicals. The vibronic emission spectra were recorded with a long path monochromator to observe vibronic bands of benzyl-type radicals in the visible region. The analysis of the spectra shows the evidence of the $o$- and $p$-chlorobenzyl radicals as typical products in corona excitation as well as the $o$- and $p$-chloro-$\alpha$-methylbenzyl radicals as unexpected species. nderline{\textbf{112}}~(51), 13427 (2008).} After subtracting the bands belonging to chlorobenzyl radicals, we could construct the vibronic emission spectra of the $o$- and $p$-chloro-$\alpha$-methylbenzyl radical in the D$_1$ $\rightarrow$ D$_0$ electronic transition at the gas phase. By comparing with those of $ab~ initio$ calculation and of the known vibrational mode frequencies with similar structures, we could obtain the electronic transition and assign the vibrational modes to the bands observed.