Photostimulated luminescence process in the x-ray storage phosphor CsBr:Ga⁺

CsBr doped with Ga⁺ has previously proved to be an efficient X-ray storage phosphor with a figure of merit comparable to that of the commercially used BaFBr:Eu²⁺. By measuring the magnetic circular dichroism of the optical absorption (MCDA), the MCDA-detected electron paramagnetic resonance and the photostimulated luminescence (PSL), the paramagnetic defect centers generated upon x-irradiation involved in the storage and read-out process were investigated and found to be particularly simple: The electron traps are F centers, the hole trap centers are Ga^{2 +} centers with a hyperfine interaction with ⁶⁹Ga of ⁶⁹A = 6.5 GHz. No superhyperfine interaction was resolved. It is proposed that the PSL-active Ga²⁺ center is an isolated Ga²⁺ on a Cs⁺ site.