Luminescence spectroscopy from the vacuum ultra-violet to the visible for Er3+ and Tm3+ in complex fluoride crystals

Abstract Spectra and decay kinetics of luminescence from several complex fluorides of alkali elements and yttrium or gadolinium doped with Er 3+ or Tm 3+ have been studied in the vacuum ultra-violet (VUV), ultra-violet (UV) and visible spectral ranges under excitation by the 157 nm radiation from a pulsed molecular F 2 -laser. It has been found that yttrium crystals have intense VUV luminescence due to interconfiguration 5d–4f transitions in the rare earth ions. On the other hand, the 5d–4f luminescence from Er 3+ or Tm 3+ in gadolinium crystals is completely absent and the nonradiative decay as a result of cross-relaxation is the dominant decay channel from the 5d level of the doping rare earth ion in these crystals. This process leads to complete conversion of absorbed VUV radiation into the lower energy part of the spectrum. These gadolinium fluorides appear to be promising materials for VUV-excited phosphors with high-quantum efficiency.