Energy transfer processes in (Lu,Gd)AlO_3:Ce

摘要

In this paper we present initial results of studies on energy transfer processes in Ce-activated Lu, Y and Gd aluminum perovskite crystals that contribute to production of scintillation light in these new scintillator materials. In particular we report and analyze emission spectra, excitation spectra, and emission time profiles under pulsed synchrotron excitation in the wavelength range of 50-300 nm. The emission spectra of Lu_(0.65)Gd_(0.35)AlO_3:Ce and Lu_(0.2)Y_(0.8)AlO_3:Ce display a characteristic double band that is due to the spin-orbit split d-f transition of Ce~(3+) with no indication of Gd~(3+) f-f emissions in the Gd-containing crystal. Nevertheless the "time-gated" and "integrated" excitation spectra of Ce-emission of this crystal in addition to the f-d Ce~(3+) bands reveal some additional fine features, absent in the Y-containing crystal, that are evidently related to the f-f transitions at Gd~(3+) ions. We also observe that the Ce-emission time profile measured under direct Ce-excitation displays fast decaying component while the Gd-tuned excitation produces slow profiles that resemble those observed under gamma or X-ray excitation. These results directly prove that slow scintillation components characteristic of the Lu_xGd_(1-x)AlO_3:Ce scintillator are due to transfer of energy that was originally deposited by the ionizing radiation in the Gd-sublattice of the crystal.