The Scintillation Mechanism in Thallium Activated Sodium Iodide

The emission and transmission of both pure and Tl activated NaI crystals have been studied as functions of wavelength and plastic deformation in the sample. The results show an increase in emission at 0.42 micron for the NaI(Tl) phosphor, and a probable decrease for the pure NaI specimen. In pure NaI three emission bands, located at 0.33, 0.375 and 0.42 micron, were observed. The 0.42 micron band in both NaI(Tl) and NaI is associated at least in part with chemical contamination of the surface. Some reduction in absorption in both the activated and pure crystals was observed upon increasing the dislocation density.