EMISSION SPECTRUM OF SUPERSONICALLY COOLED BENZYL RADICAL
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Date
1988
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Ohio State University
Abstract
The rotationally cooled gas phase electronic emission spectrum of the benzyl radical was produced with a Corona Excited Supersonic Expansion (CESE). The cooled electronic emission spectrum of the toluene precursor was also observed. Rotational temperatures were estimated to be about 15 K. This is the first observation of emission from aromatic radicals in this source. Most of the observed bands in both toluene$(^{1}B_{2}\to {^{1}}A_{1})$ and the benzyl radical $(^{2}A_{2} \to {^{2}}B_{2})$ are the result of emission from the lowest vibrational level in the electronic excited state. This suggests extensive vibrational cooling of these relatively large molecules in the CESE source. Transitions from the second electronic excited state $(2^{2}B_{2} \to {^{12}}B_{2})$ in benzyl radical were observed, although greatly reduced in intensity compared to the $(^{2}A_{2}\to {^{2}}B_{2})$ transition and previous gas phase emission spectra. The high degree of $mixing^{1}$ between $2^{2}B_{2}$ and vibronic states of $1^{2}A_{2}$ introduces a mechanism that allows collisional electronic quenching to occur during the expansion via removal of vibrational energy.
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$^{1}$ C. Cossart-Magos and S. Leach, J. Chem. Phys., 64, 4006 (1976).
Author Institution: Air Force Astronautics Laboratory/YSX., Edwards Air Force Base, CA 93523; Department of Chemistry, University of Redlands
Author Institution: Air Force Astronautics Laboratory/YSX., Edwards Air Force Base, CA 93523; Department of Chemistry, University of Redlands