Modelling of photoluminescence from F2 and F3+ colour centres in lithium fluoride irradiated at high doses by low-energy proton beams

Abstract Lithium fluoride (LiF) crystals were irradiated with a proton beam. With nominal beam energies of 3 and 7 MeV, several irradiations were performed which delivered doses ranging from 10 3 to 10 7  Gy. The ionisation produced by the protons in the LiF samples induced the stable formation in the crystalline lattice of colour centres, two types of which, the F 2 and F 3 + ones, possess broad photoluminescence bands in the red and green, respectively, when optically pumped in the blue at wavelengths close to 450 nm. At both proton energies, measurements of the distinct F 2 and F 3 + contributions to the emission spectra showed a decrease of the F 3 + integrated photoluminescence intensity at large doses, say from ∼10 6 −10 7  Gy on. We try to explain such a behaviour by assuming the formation of absorption and/or quenching centres, and compare the predictions of an ad hoc developed model with experimental data.