REFLECTANCE, LUMINESCENCE AND RAMAN EXPERIMENTS ON EU3-FIELD TRANSITIONS IN EU2BAZNO5( CRYSTAL)

Three spectroscopic techniques have been combined to resolve the compl ex problem of Eu3+ crystal held levels in Eu2BaZnO5. Eu3+ luminescence has been investigated in the off-resonance condition for several exci tation energies as a function of temperature. Raman phonons and severa l Raman crystal field transitions are obtained. From reflectance exper iments (between 1.25 and 3.7 eV), D-5 multiplet levels are determined. The schemes of the lowest electronic levels of both Eu3+ sites have b een established combining data from these three spectroscopies which s how a good agreement with the calculated values. Crystal field paramet ers are obtained in an approximation to a C-2v local symmetry. The hig h value of fourth-rank parameters indicates a partial covalent charact er of Eu-O bonds. The obtained spin-orbit coupling value, zeta = 1280( 70) cm(-1), is similar to those in other europium oxides. The variatio n of the Raman crystal field transition intensity with temperature pre sents an unexpected deviation with respect to the ground state populat ion, specially pronounced in the low temperature range. The peaks corr esponding to the three highest levels of the F-7(2) multiplet are anom alous probably due to some hybridization with the nearest oxygen level s. The relative intensity of luminescence peaks associated with transi tions from D-5(0) and D-5(1) levels vary versus temperature as a funct ion of the probability of the non-radiative decay. We propose a mechan ism that can explain the observation of anti-Stokes luminescence even at low temperatures.