Temperature Dependence of the Width and Position of theE2→A24Fluorescence Lines ofCr3+andV2+in MgO

The energy levels of an impurity ion in a solid are in general shifted and broadened by thermal vibrations of the host lattice. A study of these effects in a simple system can lead to some understanding of the phonon-impurity interaction. This paper reports measurements of the width and positions of the sharp fluorescence lines of two ${\mathrm{}\left(3d\right)\mathrm{}}^3$ ions in MgO between 4.2°K and room temperature. A semiempirical model is used to calculate the temperature dependence of the width and position from the vibrational structure associated with the sharp no-phonon line. The shift agrees well with theory but the linewidth deviates somewhat at low temperatures.