Spectroscopic properties of Pr3+ ions in a PbWO4 single crystal

Site-selective fluorescence laser spectroscopy of Pr3+ ions in lead tungstate single crystal were investigated at temperatures from 10 to 300 K. The site-selective emission spectra and fluorescence decays from the (3)p(J) (J = 0, 1, 2) and D-1(2) states were analyzed. The (3)p(J) (J = 0, 1, 2) level shows its predominantly radioactive character with the typical greenish-blue luminescence ascribed to (3)p(J) transition. The emission from the D-1(2) level is only observed when this level is directly excited. The decay kinetic of the D-1(2) level was measured under site-selective excitation and discussed in terms of cross-relaxation. The up-conversion emission from levels P-3(1) and P-3(0) following excitation of the D-1(2) state was observed in the PbWO4 crystal between 10 and 300 K. The main up-conversion mechanism, together with the understanding the quenching of the D-1(2) fluorescence in this Pr3+ heavily doped PbWO4 were discussed. The presence of the complex structures of the emission spectra and different decay profiles indicate that several processes contribute to the quenching of the D-1(2) fluorescence of Pr3+ ions. It was found that the up-conversion fluorescence intensity had a quadratic dependence on the laser input power. The temporal behavior of the up converted emission indicates that an energy-transfer up-conversion is the dominant process.