a Max-Planck-Institut für Strömungsforschung, Bunsenstraße 10, D-37073 Göttingen Germany
b Universität Göttingen, Institut für Physikalische Chemie, Tammannstraße 6, D-37073 Göttingen Germany
Abstract:
The thermal unimolecular decay of the benzyl radical has been investigated extensively by several groups. However, the reaction products could not be determined unambiguously. In this work the unimolecular bond fission of the benzyl radical is studied in a molecular beam experiment. The precursor molecules toluene and cycloheptatriene are expanded in a molecular beam and photodissociated with two photons at 248 or 193 nm, yielding in each case hot benzyl radicals. Since the internal energies lie above the dissociation limit, the benzyl radicals decay in a subsequent step. The reaction products are detected in a time-resolved manner with a quadrupole mass spectrometer on the molecular beam axis at low electron energies. The measured time-of-flight spectra provide information on the translational energy distribution of the products. In each case it is found that the hot benzyl radicals C7H7 fragment under hydrogen loss to C7H6.