Temperature dependence of the chromium(III) R1 linewidth in emerald

Abstract

The temperature dependent contribution to the R1 (2E←4A2) linewidth in emerald, Be3Al2Si6O18:Cr3, has been measured by employing spectral hole-burning, fluorescence line narrowing and conventional luminescence experiments. The contribution varies from 0.6MHz at 6.5K to ∼420GHz at 240K and the line red-shifts by ∼570GHz. Above 60K, the dependence is well described by a non-perturbative formalism for two-phonon Raman scattering. Below this temperature the direct one-phonon process between the levels of the split 2E excited state dominates. However, it appears that a localized low-energy phonon leads to a deviation from the standard pattern at lowest temperatures.