The Charge State of Copper Impurity Atoms in AgCl
<sup>67</sup> Cu( <sup>67</sup>Zn) emission Mössbauer spectroscopy and measurements of the 64Cu decay rate have shown that copper impurity atoms occupying cation sites of the AgCl lattice are in the Cu+ state when AgCl single crystals are doped with Cu by diffusion in a vacuum. By contrast, diffusion in a Cl2 atmosphere leads to partial transition of copper to the Cu <sup>2+</sup> state and to asso ciation of Cu <sup>2+</sup> with cation vacancies. The dependence of the copper impurity charge on the ambient atmosphere in annealing of AgCl crystals is explained by the effect of the atmosphere on the concentration of cation vacancies.