Studies on the Quantitative Measurements of ESR Signals The Relationship between Two-step Integral V alues and Conditions of Measurements

Abstract

It has already been reported that measuring the wave height of a two-step integral (h) gave better results for quantitative measurement of ESR signal than measuring the peak-to-peak height of the ordinary signal of derivative type (This journal, 1972, 2453). However, since signals which are recorded under different conditions cannot be compared with each other directly, this method is not simply applicable. In order to solve this problem, a method to normalize the measured values has now been examined.
The integrator used was an analogue-type dev ice with two operational amplifiers, constructed by the authors. The experimental results were as follows. With regard to the conditions of integration, "h" could be normalized by multiplying it by CiR, and C, R₂, the time constants of the first step and the second step of the integrator, and by dividing it by R₄/(R₈+R₄) and R₆/(R₅+R₆), the resistor ratio of each of the output attenuators. Moreover, "h" could a lso be normalized by dividing it by the square of the time of the integral period. Although it is generally- thought that the signal intensity can be norm alized by dividing it by the square root of microwave power (P0.5), the results, of the present experiments revealed difficulty in normalizing by dividing by Pk or log P. Therefore the microwave power should be kept constant during the measurements. Concerning other conditions of the ESR spectrometer, "h" could be normalized by dividing it by gain and modulation amplitude, but thepeak-to-peak height of a sharp signal could not be normalized when the modulations amplitude was large.
Although the peak-to-peak height of a sharp signal was strongly affected by response time change even under constant microwave power, "h" was affected very little by crystal current and response time change when the microwave power was constant. Thus, the wave heights of a two-step integral measured even under different conditions can be compared with each other provided that microwave power is kept constant.