Optical properties of trivalent chromium in silicate glasses: A study of energy levels in the crossing region

A theoretical and experimental study of the optical properties of trivalent chromium in silicate glasses is described. New experimental results presented are (1) the temperature dependence of the absorption, (2) determination of the dependence of emission on the excitation frequency, (3) determination of the 2E→4A2 emission. These results are interpreted in terms of the structure of the Cr3+ sites in the glasses. Of theoretical interest is the fact that, for Cr3+ in silicate glasses, Dq is in the crossing region of the 4T2 and 2T1 levels which interact strongly by spin--orbit coupling. To explain the absorption line shape of such systems, it is necessary to include vibronic effects. Calculations of the absorption are made and compared with experiment