Optical absorption and thermoluminescence studies in 100 MeV swift heavy ion irradiated CaF2 crystals

Research highlights: → The present paper describes the effect of Ion irradiation on optical properties of CaF2 single crystals. → The changes in Optical absorption and TL intensity with increase in ion fluence in both pure and Ytterbium doped CaF2 crystals are explained. → The defect centers responsible for the optical absorption are identified. -- Abstract: Pure and Ytterbium (Yb) doped Calcium fluoride (CaF2) single crystals were irradiated with 100 MeV Ni7+ ions for fluences in the range 5 x 1011-2.5 x 1013 ions cm-2. The irradiated crystals were characterized by Optical absorption (OA) and Thermoluminescence (TL) techniques. The OA spectra of ion irradiated pure CaF2 crystals showed a broad absorption with peak at ∼556 nm and a weak one at ∼220 nm, whereas the Yb doped crystals showed two strong absorption bands at ∼300 and 550 nm. From the study of OA spectra, the defect centers responsible for the absorption were identified. TL measurements of Ni7+ ion irradiated pure CaF2 samples indicated a strong TL glow with peak at ∼510 K. However, the Yb doped crystals showed two TL glows at ∼406 and 496 K. The OA and TL intensity were found to increase with increase of ion fluence upto 1 x 1013 ions cm-2 and thereafter it decreased with further increase of fluence. The results obtained are discussed in detail.