The relationship between quantum efficiency and average lifetime of Cr³⁺ ions in glass

For Cr³⁺ ions in crystalline hosts, in which the ⁴T₂ level is at lower energy than ²E, the variation in τ, the observed lifetime, should provide a measure of the variation in quantum efficiency. This is not the case for Cr³⁺ ions in glass; in glass the quantum efficiency falls with increasing temperature much more rapidly than the average lifetimes <τ>. We show that this is caused by the occurence in glass of Cr³⁺ ions with distinctly different non-radiative rates. We investigate this effect to see if it can provide information about the distribution of non-radiative among the Cr³⁺ ions.