Radiation induced defects in Tl⁺-doped LiF crystals

Tl⁺-doped lithium fluoride crystals exhibit very interesting properties concerning the formation of colour centres after X-rays irradiation. The presence of Tl⁺ ions, even in small concentrations, increases the number of traps which stabilize the H-centre aggregates. These H-centre aggregates become smaller and their number increases, inducing two sets of trapping levels. Photoluminescence measurements after subsequent thermal bleaching of the thermoluminescence peaks show a faster decreasing of the F₃⁺ centres, in three steps, compared with the F₂ ones. The F-H recombination processes may induce the excitation-emission transitions of Tl⁺-ions.