Pressure and temperature dependence of the emission in BaF2:Eu and SrF2:Eu

The 4f(6)5d(1)(e)-> 4f(7) emission (normal) of Eu2+ in SrF2 and normal and anomalous emissions of Eu2+ in BaF2 are studied as a function of pressure and temperature. Although in BaF2 both emissions (anomalous and normal) shift with pressure in the same spectral direction (a red shift), the anomalous emission converts to the normal emission when the pressure increases to 33 kbar. Considering the dependence of BaF2:Eu2+ luminescence on the pressure and temperature we have found that spectral transformation takes place due to a smooth pressure-induced level crossing at approximately the same pressure as the phase transition. (C) 2008 Elsevier B.V. All rights reserved.