TUNNELING DYNAMICS AND SPATIAL CORRELATIONS OF LONG-CHAIN GROWTH IN SOLID-STATE PHOTOCHLORINATION OF ETHYLENE AT LOW-TEMPERATURES

A novel method is described for preparing reactive cryocrystals by dep osition of argon-diluted reactant beams and subsequent crystallization during evaporation of the inert gas. Photochlorination of equimolecul ar ethylene-chlorine mixtures obtained by this method and studied by m eans of kinetic UV-and IR-spectroscopy reveals activationless chain gr owth with mean length 300 units in the temperature range 17-45 K. Mean chain lengths greater than 100 are observed up to the conversion degr ee of 0.6-0.7. Comparison of the experimental data with computer simul ations shows that the tunneling reaction is due to the formation of a closely packed reaction complex with high amplitudes of zero-point vib rations which lower the reaction barrier. The commensurability of reac tant and product crystal lattices results in linear propagation of cha ins without accumulation of deformation strain. The chain termination mechanism associated with the spatial correlations of chains is discus sed.