Radiation induced defects in Mn doped CaF₂

Abstract

Absorption and excitation spectra of CaF₂:Mn have been studied before and after irradiation by γ-rays in an attempt to elucidate the physical processes involved in the formation of radiation induced defects. Several new absorption bands appear in CaF₂:Mn after irradiation possibly due to the formation of Mn-F center complexes. It is difficult to attribute any of these new absorption bands to enhanced oscillator strengths in Mn²⁺. The excitation spectra consist of five bands and after irradiation a new broad band appears at 300 nm. This band exhibits fading, partial thermal annealing at 400°C complete annealing at 600°C and optical bleaching by 300 nm radiation. On the basis of these investigations we propose that perturbed F-centers in the form of Mn–F center complexes are produced in CaF₂:Mn after irradiation. Both 300 nm illumination and heating result in the destruction of the perturbed F-center and in the process Mn is excited, forming Mn²⁺∗ which decays to Mn²⁺ with 500 nm emission.