RESONANCE-ENHANCED MULTIPHOTON IONIZATION TIME-OF-FLIGHT STUDY OF CF2I2 PHOTODISSOCIATION

The resonance enhanced multiphoton ionization time-of-flight (REMPI-TO F) 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 n m 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 photofra gment translational spectroscopy. At 304 nm three competing decay chan nels were found to be operative. in decreasing order of branching, the se 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 thre e-body decay yielding CF2 +I-3/2+ I-3/2 The positive, almost maximum b eta 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.