ESR and Optical Studies on γ-Irradiated MgCl₂ Single Crystals

Abstract

The ESR spectra and the optical absorption spectra of γ-irradiated MgCl₂ single crystals, which have a layer ionic crystal structure, have been investigated. For a commercial reagent grade single crystal, an optical absorption band is found at about 3.35 eV, and a single broad magnetic resonance band in the ESR spectrum at g=2.0009±0.0009, whose width is 50±5 G. From the measurements of the isothermal decay curves of these bands, it is found that these bands originate in the same lattice defect. An trapped electron center is proposed for a model of this defect. In a sample made by recrystallization of a commercial crystal, four hyperfine structure lines are found in the ESR spectrum. By assuming an axial symmetry, the values of g_⁄⁄=2.50±0.08, g_⊥=2.29±0.05, A_⁄⁄=4600±900 MHz and A_⊥=1400±500 MHz are obtained and Cl⁰ center is proposed as a model.