Electron Paramagnetic Resonance and optical absorption spectra of Cr(III) ions in alkali cadmium borosulphate glasses

The Electron Paramagnetic Resonance (EPR) spectrum at 9.205 GHz and at 300 K has been examined for a series of Cr3+ ions doped alkali cadmium borosulphate [R(2)SO(4)-CdSO4-B2O3 (R=Li,Na,K or Cs)] glasses. The low field EPR spectral resonance lines are attributed to isolated Cr3+ ions where as the high field spectral resonance lines are attributed to exchange coupled pairs of Cr3+ ions. The absorption spectra of Cr3+ ions ions in these glasses show two broad bands characteristic of Cli ions in octahedral symmetry. The bands are slightly shifted to higher wavelength side from Li glass to Cs glass. From the optical spectra the crystal field parameter Dq and the Racah interelectronic repulsion parameters B and C are evaluated. From the EPR and optical data, it is concluded that, the site symmetry around the Cr3+ ions is octahedral and the nature of bonding is predominantly covalent in nature.