Radiation damage of chromium doped potassium alum

ESR and optical absorption studies of Cr3+ doped KAl(SO4)2 · 12 H2O show that Cr3+ is reduced to Cr2+ and Cr+ during irradiation with 35 KeV X‐rays at room temperature. In unirradiated samples the site symmetry of Cr3+ is trigonal and the impurity exbits an isotropic ESR spectrum. The g and D values of such a center are found to be 1.978 ± and 0.002 and 393 × 10−4, respectively. The irradiated crystal shows two new optical at 820 nm and another in the region 200 to 300 nm. A new additional weak isotropic ESR line is also observed in irradiated samples. The ESR line and the unresolved optical band in the region 200 to 300 nm are attributed to Cr+ centers while the 820 nm band is ascribed to Cr2+ centers. Copyright © 1976 WILEY‐VCH Verlag GmbH & Co. KGaA