On the nature of the oxygen effect in the EPR spectra of carbonized materials

It is shown that the features of the influence of O 2 molecules on the EPR spectra of carbonized materials are due their magnetic dipole-dipole interaction with carbon paramagnetic centers as being centers with different relaxation times. This circumstance explains the absence of the possibility of obtaining the required structural information when registering the EPR spectra of carbon materials having one degree of carbonization only in an atmosphere of air. For the first time, the proposed concept of a relay mechanism enables one to explain the influence of the O 2 molecules sorbed in the ultramicropores of the carbon materials on all the carbon PMC. It consists in shortening of their relaxation time and the passing away of a considerable part of the signal into the wings with an insignificant growth in the distance between the extremal points, which leads to lowering of the registered concentration of the PMC. The dependence of the nature of manifestation of the oxygen effect on the features of the porous structure makes it possible to use EPR spectroscopy for a rapid determination of carbonized materials as intermediate products when obtaining active coals.