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 (YPO4, LuPO4) doped with Nd3+, has been studied using time-resolved spectroscopy under pulsed synchrotron radiation excitation. For Nd3+, only fast (nanosecond) VUV emission due to allowed 4f(2)5d-->4f(3) interconfiguration transitions is observed in the studied spectral range (150-200 nm), while for Er3+ and Tm3+ both fast and slow (microsecond) emissions were detected. The efficiency of energy transfer from the matrix 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 transfer mechanism exists leading to a high quantum yield of the VUV emission 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.