R. Frochtenicht et M. Hartmann, HYDROGEN FORMATION IN LASER-INDUCED UNIMOLECULAR REACTIONS OF SUBSTITUTED BENZENES, Chemical physics letters, 250(2), 1996, pp. 209-216
The formation of hydrogen atoms following laser excitation of substitu
ted benzenes at 193 nm was investigated in a molecular beam experiment
. The H atom products were detected by a two-colour resonance-enhanced
two-photon ionization process. For ethylbenzene C6H5CH2CH3, r-butylbe
nzene C6H5C(CH3)(3) and benzotrifluoride C6H5CF3 specific rate constan
ts were extracted from the time dependence of H atom formation. The re
sults agree very well with former results obtained by detecting CH3/CF
3 radicals. By measurement of Doppler profiles of the H atoms we find
small mean kinetic energies. Both results indicate that the reactions
start from vibrationally excited levels of the electronic ground state
. Reaction yields between 2.6% and 13% show that hydrogen formation is
a minor but not neglectable reaction channel.