DYNAMICS FOR THE CL-]HCL+C2H5 REACTION EXAMINED THROUGH STATE-SPECIFIC ANGULAR-DISTRIBUTIONS(C2H6)

Photolysis of Cl-2 initiates the title reaction at a sharply defined c ollision energy of 0.24+/-0.03 eV. Nascent product rotational state di stributions for HCl (v=0) are determined using resonance enhanced mult iphoton ionization (REMPI), center-of-mass scattering distributions ar e measured by the core-extraction technique, and the average internal energy of the C2H5 product is deduced from the dependence of the core- extracted signal on the photolysis polarization. The HCl product has l ittle rotational excitation, but the scattering distribution is nearly isotropic. Although seemingly contradictory, both of these features c an be accounted for by using the simple line-of-centers model presente d to explain earlier results for the Cl+CH4 reaction. in contrast to t he Cl+CH4 reaction, the data suggest that the Cl+C2H6 reaction proceed s through a loosely constrained transition-state geometry. The reactio ns of atomic chlorine with ethane, C2H6, and perdeuteroethane, C2D6, y ield virtually identical results. These findings, along with the low e nergy deposited by the reaction into the ethyl product (200+/-120 cm(- 1)), demonstrate that the alkyl fragment acts largely as a spectator i n this hydrogen abstraction reaction. (C) 1996 American Institute of P hysics.