Photofragment translational spectroscopy of iodobenzene at 266 nm

The photofragmentation of C₆H₅] at 266 nm is investigated on the nuiversal crossed molecular beam ma-chine, and the translational spectroscopy as well as the angular distribution of I atom is measured. The results reveal that under the laser intensity of 10⁸ W/cm² the single-photon dissociation competes with multi-photon processes. In singlephoton dissociation the anisotropy parameter β is 0.4 and the average translational energy is only 1.04 kcal/mol, which indicates that this process is a slow predissociation. In two-photon photofragmentation the average translational energy is 51.64 kcal/mol, which accounts for about 35% of the available energy. Another photofragmentation channel is even more faster, whose peak in time-of-flight spectra corresponds to four or five photon absorptions. The branching ratio of these three channels is determined to be about 3:3:4. Project supported by the National Natural Science Foundation of China, the Youth Fund of Dalian Institute of Chemical Physics, and the Chinese Academy of Sciences.