ABSTRACT
Requirements for the EPR experimental technique are mainly determined by the tasks scheduled [256]. If one expects only to analyze if free spins exist in the sample or not, in this case, the simplest routine EPR spectrometer can be used. It can detect the presence of spins with a single line and estimate their number in the sample under study. Currently, the X-band EPR technique is the most developed and prevalent. This is due mainly to the availability starting from the 1940s of an appropriate element base and a relative simplicity of the experiments at this waveband.
