PHOTOFRAGMENTATION OF TOLUENE IN A FOURIER TRANSFORM-MASS SPECTROMETER IN THE VISIBLE AND INFRARED RANGE

The photodecomposition of the toluene ion has been measured in the visible and IR range (10 μm). Three isomers of C7H+{radical dot}8 can be distinguished, only two of them fragmenting in the IR range by loss of a hydrogen atom. One of them, the toluene ion, has to pass over an excited state that we tentatively identify as an excited cycloheptatriene radical cation. The other decomposing isomer most probably has a cycloheptatriene structure. Part of the C7H+7 ions fragments with visible light (488 nm) in a two-photon process; it is identified as benzyl ion. Tropylium is stable in this wavelength range. The dependence of these processes on the ionizing conditions, their rate constants and, where feasible, their induction time are determined. It is shown that the ratio benzylium/tropylium may depend on the cell conditions such as the filament current. © 1990.