Radiation-damage-induced defects in quartz. I. Single-crystal W-band EPR study of hole centers in an electron-irradiated quartz |
| |
Authors: | Mark J Nilges Yuanming Pan Rudolf I Mashkovtsev |
| |
Institution: | (1) Illinois EPR Research Center, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA;(2) Department of Geological Sciences, University of Saskatchewan, Saskatoon, SK, S7N 5E2, Canada;(3) Institute of Geology and Mineralogy, Siberian Branch of Russian Academy of Sciences, Novosibirsk, 630090, Russia |
| |
Abstract: | Single-crystal W-band electron paramagnetic resonance (EPR) spectra of an electron-irradiated quartz, measured at room temperature,
110 and 77 K, disclose three previously reported hole centers (#1, G and an ozonide radical). The W-band EPR spectra of these
three centers clearly resolve six magnetically nonequivalent sites each, whereas previous X- and Q-band EPR studies reported
Centers #1 and the ozonide radical to consist of only three symmetry-related components and interpreted them to reside on
twofold symmetry axes in the quartz structure. The calculated g matrices of Center #1 and the ozonide radical show that deviations from twofold symmetry axes are <10°, which are probably
attributable to distortion related to neighboring charge compensating ions. The W-band EPR spectra of Center G not only result
in improved g matrices but also allow quantitative determination of the nuclear hyperfine (A) and quadrupole (P) matrices of its 27Al hyperfine structure that was incompletely resolved before. In particular, the g-maximum and g-minimum principal axes of Center G are approximately along two pairs of O–O edges of the SiO4 tetrahedron, while the unique A principal axis is approximately along a Si–Si direction. These new spin-Hamiltonian parameters
suggest that Center G most likely involves trapping of a hole between two oxygen atoms related to a silicon vacancy and stabilized
by an Al3+ ion in the neighboring tetrahedron (hence an O2n−–Al3+ defect, where n is either 1 or 3). |
| |
Keywords: | Electron-irradiated quartz Hole centers W-band EPR spectra Symmetry 27Al hyperfine structure O2n− defects |
本文献已被 SpringerLink 等数据库收录! |
|