It was shown that optical bleaching of MA+ color centers at 80K in SrF2-Na crystals caused the core of an MA+-center to transform into the Va + Me + Va+ configuration, in which all 3 point defects were arranged diagonally in the cubic cell. Re-irradiation of an optically bleached crystal with X-rays generated FD centers within it: Va + Me + Va+ + e− → Va0 Me + Va+ ≡ FD. The FD → MA+ transformation in SrF2-Na crystals proceeded at 135K, in contrast to the FA → MA+ transformations, which took place at above 200K.

Electronic Color Centers in SrF2-Na Crystals. S.I.Kaschan, Z.P.Chornij: Physics of the Solid State, 2006, 48[2], 255-8