Electron paramagnetic resonance studies of the E′ centers in alpha-quartz

Abstract

Room-temperature electron paramagnetic resonance (EPR) studies (at ca. 9.85 GHz) of γ- and x-irradiated alpha-quartz are reported and discussed. The previously described E′2 center has been proved to be associated with hydrogen, and this center’s primary silicon-29 hyperfine coupling matrix has now been accurately determined, as were its hydrogen hyperfine coupling and electronic Zeeman splitting (g) matrices. The paramagnetic center is believed to arise from attack on a diamagnetic oxygen-anion vacancy V(O0) (E center) effectively by an electron and a proton arising from atomic hydrogen produced in the irradiation process. A second very similar center, called E′2(II) herein, was discovered and its parameter matrices too have been obtained by EPR, and it was modelled as described herein. It is proposed that the proton in E′2 resides on an oxygen anion adjacent to the vacancy species. Comparison is made of the spin-Hamiltonian parameter matrices and the choice of best symmetry-related sites expressing them, for the various centers E′1–E′4. PACS Nos.: 76.30.–v,61.72.Hh, 76.30.Mi, 42.70.Ce, 61.80.–x, 61.72.–y