Luminescence spectroscopy of CsI: Tl+

Publisher Website
Google Scholar
Abstract
Emission and excitation spectra of the phosphor CsI: Tl+ have been measured between 4·2 K and room temperature. Quenched crystals of CsI: Tl+, when excited in any of the five absorption bands that lie between 290 and 238 nm, exhibit two overlapping luminescence bands that lie at 2·19 eV (560 nm) and 2·53 eV (490 nm) at 4·2 K. A third emission band at 3·08eV (405 nm) is excited only on the long-wavelength side of the first absorption band. Peak excitation efficiency at 4·2 K is at 290 nm, whereas for the 2·19 eV principal emission it is at 280 nm. A fourth emission band at 1·78 eV (700 nm) is observed only in unquenched crystals and is therefore probably associated with (Tl+)2 dimers. The presence of three distinct emission bands which are all excited in the first (A) absorption band is a most unusual occurrence in this type of phosphor, but it is concluded that the presence of three distinct sets of minima on the adiabatic potential energy surface representing the relaxed excited A state is theoretically feasible.