Site selection spectroscopy of Cr3+ in MgAl2O4 green spinel

The optical properties of Cr3+ ions in the synthetic green spinel MgAl2O4 were re-examined by means of site selection spectroscopy. In particular, our attention was focused on the distribution of Cr3+ sites embedded in this disordered crystal. By means of site selection excitation spectroscopy, a number of Cr3+ classes associated with strong, intermediate and weak ligand field sites were identified. The fluorescence line narrowing technique was used to establish the 25 Cr3+ sites. The splitting of the 4A2 level was determined to be 1.7 cm−1. It was found that in higher concentrated samples the number of weak ligand field Cr3+ sites is increasing.