Variation of 5d-level position and emission properties of BaF2:Pr crystals -: art. no. 195112

The emission and excitation spectra of BaF2 doped with 0.3 and 3.0 mol % Pr3+ have been studied using synchrotron radiation in the range from 5 to 30 eV. In BaF2:Pr3+ (0.3 mol %) the lowest level of the 4f5d configuration of Pr3+ is located at 5.55 eV relative to the H-3(4),4f ground state. The S-1(0),4f level lies higher, at 5.77 eV. Consequently the crystal shows two types of the Pr3+ emissions, one related to 5d -> 4f transitions with a decay constant of 22 ns, another related to slow transitions from the P-3(0) level. In BaF2:Pr3+ (3.0 mol %) the lowest 5d state lies at 6.0 eV, that is above the S-1(0) level. At 10 K the crystal shows cascade emission, i.e., S-1(0)-> I-1(6) transitions followed by transitions from the P-3(0) level. At room temperature the second step of the cascade is quenched. It is shown that the energy shift of the 5d state as a function of Pr3+ concentration is due to the formation of Pr3+-based clusters at higher concentrations.