Measurement of the enhancement factor of chemically induced dynamic nuclear polarization in the photolysis of dibenzyl ketone: Determination of the spin multiplicity of the precursor

The enhancement factor of chemically induced dynamic nuclear polarization (CIDNP) in the photolysis of dibenzyl ketone is measured by using the rf pulse technique and temperature dependence of the CIDNP intensity and of the consumption rate constant. The experimental results of the enhancement factor and the yield of the cage product are then compared with the theoretical value under high magnetic field approximation. On the basis of the result, we conclude that the main precursor of the photolysis of dibenzyl ketone especially in chloroform solvent is the singlet state.