The ESR, fluorescence and selective excitation spectra of Cr3+ in three different sites of tetragonal symmetry are reported. A comparison of the intensities of the different spectra allows a correlation of the ESR and fluorescence lines to three different tetragonal centres. From the measured splittings it has been possible to deduce the magnitudes of the tetragonal components of the crystalline field used in Macfarlane's theory (1967) of Cr3+ ions. Models involving slight changes in the mechanism of charge compensation are discussed.
- excitation spectra