Absorption, fluorescence, and excitation spectra of thallium‐activated rubidium bromide

Abstract

AbstractAbsorption, excitation, and fluorescence spectra of polycrystalline RbBr: Tl phosphors are presented at various thallium concentrations. For very low thallium content two absorption bands are obtained peaking at 224 and 260 nm. Additional absorption bands appear around 230, 244 267, and 278 nm with rise of thallium content. An asymmetric fluorescence band in the ultraviolet region is obtained at low thallium concentration which can be resolved into two Gaussian emission bands peaking at 317 and 365 nm. Two additional visible fluorescence bands appear at 440 and 535 nm with rise of thallium content. The excitation spectra for the ultraviolet and visible emission bands are found to be different. Accordingly the ultraviolet emission band is attributed to the characteristic A‐emission in Tl+ monomer entering substitutionally and the visible bands are attributed to dimer centers having D4h site symmetry.