Substitution effects of methyl:: photodissociation of m-, o- and p-chlorotoluene at 266 nm

The photodissociation dynamics of m -, o - and p - chlorotoluene at 266 nm was studied using the universal crossed molecular beams machine and photofragment translational spectroscopy (PTS) technique. The time-of-flight (TOF) spectra of Cl and C7H7 photofragments were measured at different angles. By employing both forward convolution method and least-squares fitting method, the TOF spectra of photofragments ( Cl and C7H7) and the angular distribution of Cl are fitted, at the same time the translational energy distributions of photofragment and anisotropy parameters (beta) have been derived. The geometries of the ground state, the first excited state and the triplet state have been optimized using CASSCF(8,7) /6-311G** method. The transition electronic dipole moments were calculated at the CIS/6-311G* level. The calculation results are in good agreement with the experiment. Plausible photodissociation mechanisms are proposed and the substitution effects of methyl are discussed.