15min:

YOUNG WOOK YOON, CHANG SOON HUH, SANG KUK LEE, Department of Chemistry, Pusan National University, Pusan 609-735, Korea.

By means of a technique of corona excited supersonic expansion (CESE) combined with a pinhole-type glass nozzle developed in this laboratory, we generated vibronically excited but jet-cooled 2-fluoro-m-xylyl and 2-chloro-m-xylyl radicals from precursors 2-fluoro-m-xylene 2-chloro-m-xylene with a large amount of carrier gas He, respectively. The well-resolved vibronic emission spectra of the jet-cooled radical species were recorded with a long-path monochromator in the visible region. From the analysis of the spectrum, we determine an accurate electronic energy of the D₁ D₀ transition and the frequencies of vibrational modes in the ground electronic state by comparison with those of ab~ initio calculations and the known spectroscopic data of precursors for the first time. The red-shift of the origin band of each species from parental benzyl radical agrees well with those predicted from synergic effect of each substituent into benzene ring.