Vibration and Luminescence Spectroscopic Investigations of the Alkali Rare Earth Double Phosphates M3(RE,Eu)(PO4)2\mathrm{M_3 (RE,Eu)(PO_4)_2} (M=K, Rb; RE=La, Gd)

The room temperature IR- and Daman spectra of the differentM3RE(PO4)2 (M = K, Rb; RE = La, Eu, Gd) double phosphates wereanalysed and used to interpret the vibronic side band structure in the photo-luminescence spectra. The intraconfigurational 4f-4f electronic transitionsin the photoluminescence spectra of the Eu3+ doped M3RE(PO4)2 were ana-lysed in detail. The crystal field fine structure of the 5D0 -> 71',1 (J = 0-4)transitions was analysed accounting for the information on the crystal struc-ture. The effect of the temperature as well as the alkali host cation wasevaluated. Finally, a preliminary crystal field energy level scheme for the7Fj (J = 0-4) ground term was deduced from the analysis of the photo-luminescence as well as IR- and Raman spectr