Europium emission centers in CsI:Eu crystal

•The optical and luminescence properties of CsI:Eu crystals has been studied.•Several types of activator centers were revealed.•The total content of impurities in the grown crystal CsI:Eu can reach ∼10−3 mass%.•There are four main types of luminescence centers in CsI:Eu crystals.

Absorption, excitation and luminescence spectra of pure and Eu doped CsI crystals were studied depending on the activator content, excitation energy, heat treatment and X-ray irradiation. Several types of Eu2+ related centers were found. It is shown that complex centers are stable at room temperature but their structure and concentration changes at heat treatment and under irradiation. The increased content of oxygen-containing radicals was determined by IR spectroscopy in Eu-containing crystals as opposed to pure one. It is supposed that some of emission centers in CsI:Eu are caused by the presence of intrinsic (vacancy type) and extrinsic (oxygen or hydroxyl ions) defects located in the nearest environment of Eu2+ ions.