Site selection spectroscopy of Cr 3+ in MgAl 2O 4 green spinel

Abstract

The optical properties of Cr 3+ ions in the synthetic green spinel MgAl 2O 4 were re-examined by means of site selection spectroscopy. In particular, our attention was focused on the distribution of Cr 3+ sites embedded in this disordered crystal. By means of site selection excitation spectroscopy, a number of Cr 3+ classes associated with strong, intermediate and weak ligand field sites were identified. The fluorescence line narrowing technique was used to establish the 25 Cr 3+ sites. The splitting of the 4A 2 level was determined to be 1.7 cm −1. It was found that in higher concentrated samples the number of weak ligand field Cr 3+ sites is increasing.