The Ranges of Interactions in the Radiolysis of Solid Hydrocarbon Mixtures

We describe a novel technique for measuring the ranges of interaction in the radiolysis of hydrocarbon mixtures, e.g. the distance between donor and acceptor molecules in an energy transfer process. Thin layers, 20 to 1 000 Å thick, of solid c-C 6 D 12 sandwiched between other materials which activate or deactivate the hydrocarbon, are irradiated. The yields of D 2 and HD are measured as a function of the layer thickness. These yields change rapidly when the layer thickness is comparable with the range of the interaction.We find: (a) the activation of c-C 6 D 12 by n-C 6 H 14 has a very short range consistent with an ionmolecule reaction between nearest neighbor molecules; (b) the deactivation by CCl 4 or benzene has a longer range (180 Å or more) consistent with the average separation of positive ions and electrons in an irradiated hydrocarbon; (c) the intermediates in the bimolecular reaction giving HD in layers of C 6 D 12 and C 6 H 12 have a short range (< 100 Å) and cannot be thermal hydrogen atoms.