Luminescence of RbI: Tl

Emission spectra of RbI: Tl for excitation in A, B, C, and D absorption bands were measured at 4.2, 77, and 300^∘{}K. At 4.2^∘{}K, four prominent bands are observed at 3.42, 4.24, 2.82, and 2.58 eV. The 3.42- and 4.24-eV emission bands appear most prominently for A and B excitations. They are thus assigned T₁ᵤ and T₂ᵤ→A1g transitions, respectively. The 2.82- and 2.58-eV bands appear for both C and D excitations. These are also stimulated with high efficiency in the first exciton region of RbI. Both these bands are attributed to the decay of self-trapped excitons adjacent to thallium ions.