In this paper we investigate the mechanisms for electron trapping, following photoionization of Sm 2 + in γ- and non-γ-irradiated samples of Sm-doped CaF 2 . Using linear absorption, fluorescence and site-selective coherent anti-Stokes Raman excitation spectroscopy, we show that the electron traps in non-γ-irradiated CaF 2 :Sm are small clusters of trivalent Sm ions. In the γ-irradiated samples, we observe the formation of self-trapped holes after photoionization, which provides us with additional evidence for the existence of self-trapped hole pairs in γ-irradiated rare-earth-doped CaF 2 .