Electron Spin Resonance of Irradiated Quartz: Atomic Hydrogen

An electron spin resonance spectrum observed in irradiated synthetic quartz crystals is attributed to atomic hydrogen in interstitial sites. The quartz specimens were irradiated with 1.7 MeV electrons at ∼300°K (1018 electrons cm−2) and then with 60Co γ-rays (∼107 R) at ∼80°K and measurements were made without warming. The hydrogen spectra had a hyperfine constant A = 521.3 Oe (1453.1 Mc/sec) when the applied field was along the crystal threefold axis. An anisotropy of the hyperfine interaction of the order of 0.75 Oe was detected. The g value was 2.0021±0.0005 and evidence for a small variation in this value with rotation was inferred. There are three sites for the atomic hydrogen in the unit cell which are related by the three fold symmetry operator of the crystal and which are otherwise equivalent. Additional hyperfine interactions with 29Si nuclei were also observed enabling a tentative model of the sites to be proposed. The width of the line was 0.1 Oe and was attributed mainly to field inhomogeneity. Another spectrum was observed with a slightly smaller hyperfine interaction and was also attributed to atomic hydrogen in a different interstitial site. Detailed measurements were not made due to the low intensity of the spectrum.