MULTIBAND ELECTRON-SPIN-RESONANCE SPECTROSCOPY OF RARE-EARTH S-IONS IN GLASSES - THE ISOSPECTRAL FREQUENCY RATIO METHOD

Results of ESR studies of the rare-earth S ions Gd3+ and Eu2+ in oxide glasses at various microwave frequencies in the range 2.7-10.3 GHz are presented. The spectra of two different centres (different ions or the same ion in different glasses), obtained separately and with appropriately chosen frequencies nu-1 and nu-2, respectively, coincide after being normalized with respect to both the frequency and the maximum absorption intensity. The isospectral frequency ratio (IFR) nu-1/nu-2 remains constant for a given pair of centres. It is shown that for such centres the ratio of each pair of equivalent fine-structure (FS) parameters is equal to the IFR. Therefore, if the FS parameters are determined for a rate-earth S ion in a certain glassy matrix, these parameters can be readily obtained in all cases, when the IFR can be determined.