FAST VUV EMISSION OF RARE-EARTH IONS (ND3+, ER3+, TM3+) IN WIDE BANDGAP CRYSTALS

The VUV emission of several wide bandgap crystals (BaY2F8, LiYF4, SrF2 , BaF2) doped with Er3+ and Tm3+, stoichiometric ErF3 and TmF3, and (Y PO4, LuPO4) doped with Nd3+, has been studied using time-resolved spec troscopy under pulsed synchrotron radiation excitation. For Nd3+, only fast (nanosecond) VUV emission due to allowed 4f(2)5d-->4f(3) interco nfiguration transitions is observed in the studied spectral range (150 -200 nm), while for Er3+ and Tm3+ both fast and slow (microsecond) emi ssions were detected. The efficiency of energy transfer from the matri x to the rare earth ion is very low in all fluoride crystals studied, while in YPO4 and LuPO4 doped with Nd3+ a very efficient energy transf er mechanism exists leading to a high quantum yield of the VUV emissio n for these compounds. On high-energy excitation the decay kinetics of the 5d-->4f emission become non-exponential and both the acceleration and delay of the decay can be observed for the particular material. ( C) 1998 Elsevier Science S.A.