TRANSLATIONAL DIFFUSION OF A TRANSIENT RADICAL STUDIED BY THE TRANSIENT GRATING METHOD, PYRAZINYL RADICAL IN 2-PROPANOL

A translational diffusion coefficient (D(diff)) of a transient radical created by a photochemical reaction of pyrazine, in 2-propanol is measured by the transient grating technique. The rise and decay curves of the transient grating signal on the millisecond time scale are attributed to the diffusion of the pyrazinyl radical and the parent molecule (pyrazine). D(diff) of both species are determined. The measured D(diff) of the radical is four times smaller than that of pyrazine even though the molecular size is similar to each other. The small D(diff) suggests that the radical-solvent interaction is stronger than the parent molecule-solvent interaction.