Luminescence characteristics of Tl ions co-doped RbCl:Eu crystals

RbCl:Eu²⁺ single crystals which are co-doped with thallium display characteristic Eu²⁺ emission around 420 nm and additional emission band at 312 nm with a weak shoulder around 390 nm attributable to centers involving Tl⁺ ions. Additional excitation and emission bands observed in Tl⁺ doped RbCl:Eu²⁺ single crystals are attributed to the presence of Eu²⁺ aggregates and complex centres involving both Eu²⁺ and Tl⁺ ions. Inclusion of Tl⁺ ions in RbCl:Eu²⁺ crystals is found to enhance the intensity of Eu²⁺ emission at 420 nm due to an energy transfer from Tl⁺ → Eu²⁺ ions.