EVIDENCE FOR ELECTRON TRAPPING BY SM DIMER AND TRIMER CENTERS IN SM DOPED CAF2

Using coherent anti-Stokes Raman and linear absorption spectroscopy we present experimental evidence for a novel electron trapping mechanism in Sm doped CaF2. The appearance of additional Raman lines after ioni zation of the Sm2+ ions, their dependence on the Sm3+ concentration an d their behavior due to an enhancement by the lowest 4f-->5d transitio n of Sm2+, support strongly that electrons can be trapped by dimers or trimers of Sm3+ ions in a CaF2 lattice. The resulting color change is reversible due to a possible reionization of the traps, rendering thi s material photochromic. (C) 1996 American Institute of Physics.