The Recombination of Iodine Atoms in Solution

Abstract

A simple theory involving jumps between lattice sites has been used to treat the recombination of atoms produced in solution by photo‐chemical dissociation. The results have been applied to experimental data obtained previously on the photo‐dissociation of iodine in hexane at 25°C. The treatment indicates that if a pair of atoms is separated by one molecular diameter in the dissociation process, then the probability is 0.40 to 0.50 that these atoms will recombine by diffusion in a period of 10⁻⁶ second or less. The experimental data for light of 436 mμ indicate that if some of the atoms undergo ``primary recombination'' without escaping from the cage of solvent molecules in which they are formed, then a larger number of atoms must become separated by two or more molecular diameters as a result of the photo‐dissociation. For light of 578 mμ the data and calculations indicate that about 35 percent of the atoms become completely separated and ultimately combine with atoms from other molecules, about 30 percent become separated by a molecular diameter but recombine rapidly by diffusion, and about 35 percent either fail to undergo predissociation or recombine without escaping from the cage of solvent molecules in which they are formed.