Optical and Scintillation Properties of NaI(Tl) Crystals

Using absorption spectroscopy and luminescent methods, we have investigated qualitatively dissimilar NaI and NaI(Tl) crystals. It is established that in NaI(Tl) crystals grown under conditions of melt hydrolysis and interaction with the air components, centers of additional luminescence of nonactivation nature are formed that decrease the transparency in the activator-radiation region. Data on the hole nature of these centers are obtained. It is shown that high-temperature annealing can alter the number of centers responsible for the decrease in the transparency of the NaI(Tl) crystals.