Three previously unreported paramagnetic centers generated by ionizing radiation in germanium-doped quartz have been investigated by electron-paramagnetic-resonance (EPR) techniques. The defects responsible for the three distinct EPR spectra are structurally similar. Anisotropic spectroscopic analysis and monovalent-ion-exchange experiments have been interpreted in terms of an unpaired electronic spin-1/2 configuration localized in the vicinity of a silicon-substituted germanium impurity and three interstitial alkali impurities (combinations of Na and Li). Within this model, the principal differences among the three centers are the specific combination of Na and Li impurities involved in the defect structure. The principal spectroscopic differences among the three centers are the magnitudes of the $g$ shifts and hyperfine-interaction energies.

• Received 7 May 1973

DOI:https://doi.org/10.1103/PhysRevB.8.4833