EXAMINATION OF ALLYL RADICAL EXCITED-STATE DYNAMICS AND GROUND-STATE VIBRATIONAL FREQUENCIES BY ULTRAVIOLET RESONANCE RAMAN-SPECTROSCOPY

The first Raman spectra of the allyl radical have been obtained. The intensities of the observed Raman spectra indicate excited-state dynamics consistent with a disrotary photoisomerization of the allyl radical to form a cyclopropyl radical. Prior to this work, direct examination of the photoisomerization pathway was not possible due to limitations of the techniques applied. The ground-state vibrational frequencies observed are found to be in excellent agreement with recent theoretical calculations suggesting a reassignment of the literature infrared frequencies. This work demonstrates that resonance Raman spectroscopy is a powerful method for examination of gas-phase free radicals.