Ion recombination processes in rigid solutions

It is known that the free ion yield is small in irradiated aromatic hydrocarbon liquids. This study uses pulse radiolysis to observe anions of aromatic solutes in matrices at 77 K. In aliphatic matrices, trapped electrons tunnel to aromatic solutes and the anion yield is observed to grow with time. If the concentration of aromatic solute is large (0.1 M) or if the matrix is aromatic, ion recombination via tunneling dominates the anion kinetics, and long lived triplet states are observed to grow in. These results and the effects of other charge scavengers indicate that just a few percent of added aromatic material can dramatically increase the probability of charge recombination in aliphatic media, and that this effect involves decreased charge separation distances. The same effect apparently also occurs in alkane liquids at room temperature.