Beschreibung:
In undoped crystals of MgO, x irradiation converts a large fraction of Cr3+ in octahedral symmetry to Cr2+. Heating such crystals until a blue thermoluminescence has been observed causes further reduction. Usually 95% or more of the Cr3+ is converted by the combined treatments. However, in Cr-doped MgO one is able to reduce only a small fraction of the octahedral chromium to Cr2+. The Cr2+ is reconverted to Cr3+ by heating. ESR measurements show that in the same temperature interval nearly all of the Fe1+ formed on x irradiation has disappeared. The source of electrons acquired by Cr3+ thus appears to be the Fe1+ ions. The thermoluminescence is ascribed to the Cr3+-electron interaction, as suggested by Hansler and Segelken.