Energy transfer and sensitised luminescence in single crystals of CaF₂:(Ce+Mn) system

Abstract

The measurement of absorption, luminescence, and relative intensity of cerium and manganese emission during fluorescence, on single crystals of CaF₂:(Ce+Mn), have been reported in this paper. The occurence of the absorption bands have been explained in the following manner: (i) 250 mu band due to the transfer transition from F⁻ to²D, the excited state of Ce³⁺, (ii) 305 mμ band due to the characteristic transition of Ce³⁺ and (iii) 335 mμ band due to the perturbed level of the lattice. The emission bands have been explained like this, (i) 320 and 340 mμ bands due to the transitions of²D to²F_5/2,7/2 levels of Ce³⁺ (ii) 380 and 440 mμ bands corresponding to the perturbed levels and (iii) 520 mμ band due to transfer of energy from cerium centres to manganese centres. The results of the present investigation indicate that energy transfer in this system occures not only from cerium to manganese centres but also from cerium to cerium and cerium to perturbed levels of the lattice. It has also been observed that energy transfer process is temperature dependent in this case. An energy level scheme is proposed to explain the transfer mechanism.