Luminescence properties of KCl:Ag− crystals excited near the fundamental absorption edge

► We study the luminescence properties of KCl single crystals doped with Ag− ions. ► The excitation around the absorption edge induces a broad luminescence at 2.60 eV. ► The 2.60 eV luminescence is attributed to the exciton localized at the Ag− ion. ► The localized exciton has the two-center type configuration of the relaxed exciton.