Abstract: We observed the difference between the ST-ESR spectra caused by the difference of the dielectric properties of the samples directly. Then we tried to eliminate these differences and the error of the measured τ_C caused by them by using the "power compensation" method. We also studied the effects of the dielectric property of the sample in the whole range in which the ST-ESR spectra are sensitive to τ_C. The results show that the error of the measured τ_C is large and it is necessary to eliminate the error by using the "power compensation" method when we make use of the ST-ESR method.

Key words: ESR, Spin labeling, Rotational correlation time, ST-ESR