F centre production in CsI and CsI ± Tl crystals under Kr ion irradiation at 15

We present results of simultaneous in situ luminescence and optical absorption studies in scintillator CsI and CsI±Tl crystals, exposed to very dense electronic excitations induced by Kr ions (8.63 MeV/amu). Irradiation at 15 K leads to the formation of the prominent F absorption band. In addition, several other features of the broad absorption between exciton and F bands were ascribed to an anion vacancy, a centre (240 nm), self-trapped hole, Vk centre (410 nm) and interstitials, H centres (560 nm). We have found that low doping of thallium ( 10 cmÿ3) causes the F centre formation to proceed more rapidly than in pure crystal. On the other hand, we were not able to create any amount of F centres in heavily doped CsI±Tl. We have shown that point defects created by heavy ions manifested themselves in luminescence ageing. Ó 2000 Elsevier Science B.V. All rights reserved. PACS: 61.72.Ji; 61.80.Jh