Search

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 (β) 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.

The ultraviolet photodissociation of nitrosobenzene at 266 nm has been performed on a universal crossed molecular beams machine with a TOFMS detector. The time-of-flight spectra of the NO and C6H5 photofragments have been measured. The TOF spectra evidence only one component. The measured photofragment translational energy distribution P(E-t) reveals that about 29% of the available energy is partitioned into translational energy. The anisotropy parameter beta at this wavelength is -0.64. From P(E-t) and beta, we deduce that during the photodissociation of C6H5NO, a perpendicular transition dominates over a parallel transition. Ab initio calculations were also performed to interpret the mechanism of the photodissociation.

The photodissociation o -dichlorobenzene at 266 nm has been investigated using the universal crossed molecular beam technique. Photofragment translational energy distribution P ( E t ) and angular distribution of photofragments have been obtained and it is estimated that 23% of the available energy is assigned to translational energy. The anisotropy parameter is determined to be 0.4. From P ( E t ) and β we deduce that o -C 6 H 4 Cl 2 photodissociation is a slow process. Ab initio calculation has been performed and it shows that the parent molecule has a larger geometry deformation in its excited states comparing with that of the ground state. The possible dissociation mechanism has also been proposed.