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Optical storage studies on the trapping states of BaFCl:Eu2+

The optical absorption spectra of BaF2−xClx:Eu in different states of optical storage were measured to clarify the electron trapping mechanism for its optical storage and photo-stimulated luminescence (PSL). Based on the absorption spectra and difference absorption spectra, the electron transfer processes after ultraviolet (UV) light irradiation were investigated. This demonstrates that (1) Eu3+ ions are formed upon UV light irradiation at room temperature; (2) the two absorption bands in the visible region (400–600 nm) should be assigned to two different F centres, both of which contribute to the optical storage and PSL, and (3) a third broad difference absorption band around ∼ 650 nm, which matches the common laser better, was observed.