THE EFFECT OF THE COULOMB FORCE ON THE DIFFUSIONAL MOTION OF RADICALS AS STUDIED BY THE SOLVENT PERMITTIVITY DEPENDENCE OF THE CIDNP INTENSITY

The diffusional motion of radical ions in the photoisomerization of trans-stilbene in the presence of triphenylamine is studied by the solvent permittivity dependence of the CIDNP intensity. The CIDNP intensity is analyzed with a stochastic Liouville equation that includes the effect of the Coulomb force on the diffusional motion of radicals. The Coulomb force greatly affects the diffusional motion. The increase of the Coulomb force enhances the reaction yield in the high-permittivity region (epsilon(r) > 12), and suppresses the reaction yield in the low-permittivity region (epsilon(r) < 12).