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 ionization of the Sm2+ ions, their dependence on the Sm3+ concentration and their behavior due to an enhancement by the lowest 4f→5d transition 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 this material photochromic. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]