REDUCED DIMENSIONALITY QUANTUM SCATTERING CALCULATIONS ON THE CL-]HCL+CH3 REACTION(CH4)

Reduced dimensionality quantum scattering calculations using the Rotat ing Line Approximation, RLA, are performed on the Cl+CH4-->HCl+CH3 rea ction, treating CH4 as a pseudo-diatom QH. A LEPS potential energy sur face is used, where the zero-point energy of the modes not explicitly treated in the RLA calculations are included. The calculations are per formed using hyperspherical coordinates and the improved log-derivativ e method of Manolopoulos. Boundary conditions have been applied using a hyperspherical projection method and an approximate method where the boundary conditions are applied directly in the hyperspherical coordi nates. It is explicitly shown that the agreement between the methods i s good. Scattering resonances are observed and related to the shape of the hyperspherical adiabats. Cumulative and state-to-state reaction p robabilities are also presented. Vibrational adiabaticity is found to dominate without being exclusive. For Cl+CH4(upsilon =1)-->HCl(n=1)+CH 3 and a translational energy of 0.159 eV, measured differential cross sections give predominantly forward scattering, while for Cl+CH4(upsil on = 1)-->HCl(n = 0) + CH3 there is predominantly backward and sideway s scattering. Our calculated differential cross sections are in agreem ent with these general observations. Thermal rate constants have been calculated for the temperature range 200-800 K, The calculated rate co nstants are smaller than the experimental ones by less than 40% over t he entire temperature range. (C) 1998 American Institute of Physics.