The absorption spectra of Sm3+and Sm2+in CaF2have been measured from 200–800 m&mgr; at room and liquid‐nitrogen temperatures. A strong divalent absorption band at 620 m&mgr; has an effective oscillator strength of 1.1×10−2. This band has been used to study the reduction of CaF2:Sm3+by ionizing radiation. For some samples, the reduction is as large as 50%. The kinetics of the reduction is obscured due to the presence of oxygen and other crystal defects. The data do indicate that the charge compensator for Sm3+in CaF2is an interstitial F−ion.