STUDY OF THE LINEWIDTH OF THE CIDNP-DETECTED ESR-SPECTRUM

Microwave-power dependence of the linewidth of the CIDNP-detected ESR spectrum in the photolysis of p-benzoquinone has been investigated. The linewidth of the dynamic nuclear polarization spectrum increases with increase of the microwave power, whereas that of the stimulated nuclear polarization spectrum is almost independent of the power. These observations indicate that the linewidth of the dynamic nuclear polarization (DNP) spectrum is governed by the microwave power, and that the broad feature of the stimulated nuclear polarization (SNP) spectrum comes from the short lifetime of the intermediate radical pair.