The Temperature and Pressure Dependence of the Emission Spectrum of Alexandrite.

The emission spectrum of alexandrite, BeAl(,2)O(,4):Cr('3+), has been studied over the temperature range 8 K to 300 K and the pressure range 0 kilobar to 40 kilobars. Temperature dependence effects are accounted for by thermalization among the excited states and interactions of the chromium impurities with lattice vibrations. The important role of anharmonic forces is noted in explaining the linear shifts of th R line energies with applied hydrostatic pressure. In addition, the effects of hydrostatic pressure on the widths and intensities of the R lines is also considered.