Some Optical Properties of Lead Activated Potassium Halide Phosphors

Abstract

Absorption, emission and excitation spectra of KCl:Pb and KBr:Pb have been measured at various temperatures. These observed spectra are similar to those of KCl:Tl, and the absorption bands seemed to be due to transitions in Pb⁺⁺ ions which occupies the normal positive ion sites. The two principal excited states are ¹P₁ and ³P₁ of Pb⁺⁺ ion. 273 mμ absorption, 345 mμ emission in KCl:Pb and 302 mμ absorption, 365 mμ emission in KBr:Pb are attributed to ³P₁–¹S₀ transitions perturbed by surrounding host lattice ions. The excitation to ¹P₁ state does not manifest any dstinct emission which is different from the case of Tl activated phosphors. The near ultra-violet emission suffers violent thermal quenching at room temperature, and the activation energies of these non-radiative process are found to be 0.28 eV and 0.18 eV for KCl:Pb and KBr:Pb, respectively.
Several discussions using a single configuration coordinate model are given.