Measuring method of longitudinally detected ESR signal intensities against resonant frequencies at 250 to 950 MHz in a constant microwave field

Signal intensities of longitudinally detected ESR (LODESR) of 1,1-diphenyl-2-picrylhydrazyl powder were precisely measured at 250 to 950 MHz under a constant magnetic field microwave that was applied using a single-turn coil. The LODESR signal intensity was reduced linearly due to smaller Zeeman splitting. Because the noise level was constant, the sensitivity of LODESR was approximately proportional to the resonant frequency. As far as we know, this study represents the first attempt to measure precisely the relationship between the signal intensities and resonant frequencies of ESR in an experimental condition.