Resonance enhanced multiphoton ionization time-of-flight study of CF2I2 photodissociation

The resonance enhanced multiphoton ionization time-of-flight (REMPI-TOF) technique was applied to study the complex dissociation of CF2I2 in a supersonic expansion. Using nanosecond excitation at 248, 266, and 304 nm and probing the I-3/2 and/or I-1/2 photoproducts, we determined the photofragment speed distribution, the recoil anisotropy parameter beta and the branching ratio for each of the decay channels. At 248 nm the dissociation proceeds according to a concerted three-body decay, (CF2I2-->CF2)-C-hv+I-1/2+I-3/2 (90%) or CF2I2-->(CF2)-C-hv + I-3/2+ I-3/2 (10%) consistent with our previous results obtained from photofragment translational spectroscopy. At 304 nm three competing decay channels were found to be operative. in decreasing order of branching, these are: two-body decay to CF2I + I-1/2,I- sequential three-body decay CF2I2-->(CF2I)-C-hv + I3/2-->CF2 + I-3/2+I-3/2,I- and a concerted three-body decay yielding CF2 +I-3/2+ I-3/2 The positive, almost maximum beta values observed for all the primary steps in the 248, 266 and 304 nm photodissociation imply that the excited stales which subsequently lead to dissociation are exclusively of beta(1) symmetry and that the primary bond-breaking processes occur on a subpicosecond time scale. (C) 1998 American Institute of Physics.