Analysis of temperature dependence of efficiency of infrared radiation transformation into visible in YF3:Yb,Er system

The temperature effect on the efficiency of transforming infrared radiation into visible in the YF3:Yb, Er system has been theoretically analyzed. It is shown that temperature dependence of the transformation efficiency is caused by temperature dependence of probabilities of multiphonon processes of radiationless relaxation and electron excitation energy transfer. A conclusion is made that optical modes with intermediate frequencies of the phonon spectrum of the base lattice and values of wave vectors in the vicinity of the Brillouin zone centers participate in multiphonon processes