TEMPERATURE-DEPENDENCE OF THE LUMINESCENCE FROM HEAVILY-DOPED RUBY

Ruby, with a high concentration of chromium ions, emits sharp line emi ssion from single ions and from exchange-coupled ion pairs. Large vari ations in the intensities and lifetimes of these sharp lines are obser ved, when the temperature is varied (X.X. Zhang et al., J. Lumin. 48 & 49 (1991) 248). These variations can be understood if one takes into account that at high dopant levels clusters of chromium ions are forme d, efficient excitation transfer can occur between the clusters and th e single ions, and these clusters can act as a reservoir of optical ex citation in the ruby crystal.