PHOTOFRAGMENT TRANSLATIONAL SPECTROSCOPY OF FLUORINATED HALOMETHANES

The primary and secondary dissociation processes of CF2Br2 and CF2BrI have been studied by photofragment translational spectroscopy in a pul sed molecular beam. The photolysis of CF2Br2 at 193 nm produces mainly the fragment pair CF2Br + Br and, in a competing primary process, CF2 + Br2. The CF2Br radicals are formed with sufficient internal energy to overcome the barrier of the unimolecular secondary dissociation to CF2 + Br. The photodissociation of CF2BrI at 248 nm also proceeds alon g two decay pathways involving the fission of the weak C-I bond and th e stronger C-Br bond, respectively. The former reaction produces spin- orbit excited iodine atoms I(2P1/2) and stable CF2Br radicals, whereas the latter reaction produces unstable CF2I radicals. The results of t his study are compared with those of other workers, and an account of the ultraviolet photochemistry of fluorinated halomethanes is given.