Luminescence of a thallium-perturbed on-centre self-trapped exciton in CsCl:Tl crystal

In the luminescence spectrum of a thallium centre in CsCl:Tl crystal, besides two ultraviolet bands of the Tl+ ion and two visible bands belonging to the off-centre self-trapped exciton perturbed by the Tl+ ion, an additional band peaking at 4.56 eV has been observed at the 6.1 eV excitation. The decay kinetics and polarization of this emission have been studied. On the basis of the results obtained, the 4.56 eV emission is ascribed to a type I (on-centre) self-trapped exciton perturbed by the Tl+ ion.