The vacuum ultraviolet photodissociation of the chlorofluorocarbons. Photolysis of CF₃Cl, CF₂Cl₂, and CFCl ₃ at 187, 125, and 118 nm

Photofragmentation of the chlorofluorocarbons, CF₃Cl, CF ₂Cl₂, and CFCl₃, was investigated at 187, 125, and 118 nm using VUV harmonic generation techniques and (2+1) resonantly enhanced multiphoton ionization detection of ground Cl(²P _3/2⁰) and excited Cl*(²P _1/2⁰) state fragment atoms. Product translational energy and angular distributions were derived from Cl⁺ arrival time distributions obtained by time-of-flight mass spectrometry. Photolysis of CF₃Cl at 125 and 118 nm takes place via the 4s(a¹) and 4p(e) Rydberg states, respectively, and two primary fragmentation channels are observed. A "slow" channel with a most probable center-of-mass (c.m.) translational energy near zero is assigned to the production CF₃ ^* radicals in the 2A′₁, 2A″₂, and 1E′ electronically excited states. The second Cl/Cl^* fragmentation channel has a c.m. translational energy distribution peaked at E_tr≥1 eV and is tentatively assigned to a sequential dissociation process in which rapid C - Cl single bond rupture is followed by a secondary fragmentation of CF₃^* to CF₂+F. The time-of-flight (TOF) spectra for CF₂Cl₂ and CFCl ₃ following excitation at 125 and 118 nm suggest that concerted three-body fragmentation involving the loss of two Cl/Cl^* atoms is the dominant dissociation process. By contrast, photolysis of CF ₂Cl₂ and CFCl₃ at 187 nm results in structured Cl⁺ arrival time distributions which are used to derive translational energy distributions and asymmetry parameters. Simulations of the TOF spectra suggest the presence of three Cl/Cl^* fragment channels, with the highest energy channel clearly attributable to single C - Cl bond rupture leading to internally excited molecular fragments. The contribution of sequential and simultaneous two-Cl loss processes to the low translational energy channels is also discussed.