Physics of halide scintillators

The paper reviews the results obtained within the last 5-6 years in the fie ld of the physics of some halide crystals which have led to a better unders tanding of their characteristics. The luminescence and scintillation charac teristics of caesium iodides, widely used in the existing detectors, as wel l as the properties of some other selected materials are discussed in view of their possible applications. For all the systems concerned, the emission important for their practical applications arises from the radiative decay of excitons of various types. The following features are considered in mor e detail: (1) the excited states structure, the mechanism of excitation of the localized exciton emission in the impurity-induced absorption bands, th e processes of defects creation, and the scintillation mechanism in CsI:Tl and CsI:Na scintillators; (2) the luminescence of on-centre excitons in CsI and Rbl crystals; (3) the luminescence of free cation excitons in the CsPb X3-type aggregates thermally created in CsX:Pb single crystals (X = Cl, Br) ; (4) the model of the excited states responsible for the cation exciton lu minescence of lead halides. (C) 2001 Elsevier Science Ltd. All rights reser ved.