High field CIDNP. general analytic results

The radical pair theory of chemically induced dynamic nuclear polarization (CIDNP) in high magnetic field has been reexamined using an analytic approach. General expressions can be given for the spin dependent probability of reaction. These expressions are independent of the diffusive behavior of the radicals and can thus be applied to any diffusion model. We have applied these results to the three-dimensional continuous diffusion model and derived analytic expressions that permit a simple and accurate calculation of CIDNP polarization for all diffusional rates and all magnitudes of the magnetic interactions. The results are exact for a short range exchange interaction and the results for the combination of a long-range exchange interaction and slow diffusion are within 10% of the published numerical solutions. Exact analytic expressions are also given for the case where a scavenging reaction is present.