Effect of γ‐Irradiation on Eu²⁺ Ions in KCl Crystals

Optical absorption and emission, EPR, ITC, and thermoluminescence spectra of RT γ‐irradiated KCl:Eu²⁺ crystals are examined. ITC and EPR measurements of heavily irradiated samples point to the lack of any I.V. Eu²⁺ dipoles. Examination of optical properties permits to exclude the presence of Eu⁺ and Eu³⁺ ions. On the other hand, the examination of thermal annealing effects in heavily irradiated samples reveals the lack of any correlation between the recovery of original europium dipoles and the decay of colour centres. The results obtained can be understood by assuming radiation field induced aggregation of europium dipoles.