Bleaching of Sm2+ during photoluminescence and cathodoluminescence

Photoluminescence (PL) can trace Sm2+ and Sm3+ in different host lattices. Reversible bleaching of the Sm2+ luminescence is reported for high intensit y excited FL, leaving the Sm3+ luminescence unchanged. The power dependent bleaching efficiency of the Sm2+ luminescence was investigated for single c rystals of CaF2, SrF2, BaFCl, SrFCl, SrFCl0.85Br0.15, SrB4O7 and ceramic sa mples of BaCl2, SrSO4. Photoconductivity of SrFCl:Sm2+ bears evidence for a n excited state absorption (ESA) to the conduction band of electrons origin ating from the 5d level of Sm2+. We assume a nonradiative decay of these el ectrons to the ground state of Sm2+. This process may prohibit a Sm2+ lumin escence for D-5(J) --> F-7(J). BY Cathodoluminescence (CL) predominantly Sm 3+ was observed, because the excitation by electrons converted Sm2+ into Sm 3+. Among investigated host lattices some showed an almost complete transfo rmation into Sm3+ and others featured a residual Sm2+ CL intensity. (C) 200 1 Elsevier Science B.V. All rights reserved.