DYNAMICS OF MULTIDIMENSIONAL NUCLEAR TUNNELING IN THE CHAIN-ETHYLENE CHLORINATION AT LIQUID-HELIUM TEMPERATURE

The structure of the mixed ethylene-chlorine 1:1 crystal, and the reactive center which forms in this crystal due to ethylene-chain chlorination and consists of the radical C2H4Cl and the molecule Cl2, are calculated by means of intermolecular-interaction-energy minimization. The lattice deformation created in previous processes of chain growth results in a shortening of the C-Cl distance between C2H4Cl and Cl2 to 3.2 angstrom, as compared to the equilibrium van der Waals distance of 3.6 angstrom, and reduces the barrier height for conversion in the reactive center. The tunneling is shown to take place through a vibrational-adiabatic barrier of the three-dimensional PES, taking into account two intra- and one inter-molecular vibrations. This barrier height is 1.5 kcal/mol, and the tunneling length and mass are 0.55 angstrom and 17 m(H) respectively. The rate constant at T = 0 is 10(2) s-1, in accordance with experimental data.