Chromium centres in 3 CdSO<inf>4</inf> · 8 H<inf>2</inf>O single crystals

The optical absorption spectra of 3 CdSO4 · 8 H2O single crystals doped with Cr3+ is recorded at 300 and 80 K; the crystal field transitions are assigned and the B, C, Dq parameters evaluated. Polarisation investigations are undertaken to establish the exact electric dipole transitions and the exact magnetic dipole transitions. Splitting of the bands (differences between the parallel and perpendicular polarised spectra) due to the non‐cubic fields acting on the chromium (III) ion are not observed though two inequivalent cadmium atoms exist in the lattice. Also no lowering of symmetry is observed either from the low temperature spectra or the polarised spectra. Radiation damage studies are undertaken to study the mechanism of the formation of Cr3+ to Cr+ and the valence state effect on the electronic transitions. The effect of space charge compensating vacancies on the electronic transitions and its effect on the crystal field strength is studied using the radiation damage spectra. The formation of Cr+ from Cr3+ through Cr2+ is well explained. The theoretically calculated values coincide well with the experimentally observed values for the octahedral symmetry for both, Cr3+ and Cr+ ions in 3 CdSO4 · 8 H2O lattice. Copyright © 1989 WILEY‐VCH Verlag GmbH & Co. KGaA