Reversible photochromic processes in BaClF : Sm2+

The fluorescence intensity of Sm2+ in BaClF has been found to decrease with the 325-nm light of a He–Cd laser and to recover with the 488-nm light of an Ar+ ion laser at room temperature. At the same time, the increase or decrease in the optical absorption due to F centers has been observed. These results are interpreted in terms that Sm2+ is photoionized to Sm3+ by the 325-nm light and the excited electrons are captured by halogen vacancies of BaClF, while the trapped electrons are released under the 488-nm light and Sm3+ is reduced to Sm2+. These findings indicate that BaClF : Sm2+ satisfies conditions of the novel optical memory using photobleaching and multiple light scattering. However, it has been found that the rate of the decrease in the Sm2+ fluorescence intensity is insensitive to the 325-nm exciting laser power. The photoionization mechanism in this material will be discussed.