Description:
<jats:title>Abstract</jats:title><jats:p>The formation of colour centers at 200 K in γ‐irradiated KCl crystals doped with Eu<jats:sup>2+</jats:sup> ions in a wide concentration range is studied by optical absorption, EPR, and ITC method. The EPR and ITC measurements reveal the drastic decrease of concentration of isolated europium dipoles induced by irradiation at 200 K. Moreover, no correlation between concentration changes of colour centers and Eu<jats:sup>2+</jats:sup> dipoles induced by irradiation and postirradiated annealing has been found. The results obtained are explained by radiation stimulated aggregation of Eu<jats:sup>2+</jats:sup> dipoles into small clusters at 200 K.</jats:p>