EPR characterization in natural quartz samples of a newly discovered hydrogen related defect and already known germanium related defects

Abstract

The role of hydrogen in the formation and modification of defects in quartz is well known, but still to be clarified is its involvement in trapping and recombination properties of quartz on which its dating characteristics are based. In this work, we studied the thermal stabilities of EPR signals in natural pegmatitic quartz using an X-band spectrometer. We also observed at least two previously unreported EPR signals in quartz, one of them possessing a hydrogen hyperfine structure with large coupling constant. Its thermal stability is intermediate between the well-known [GeO4]- and [GeO4/Li+]0 centres, while the other newly reported signals possess a thermal stability comparable to the latter. The sample has been further studied with a Q-band spectrometer to enhance the resolution of the spectrum. This allowed to confirm, without having to fit or simulate the overlapped signals, the g-factors reported in the literature for Ge related centres, which are strongly overlapped in the X-band. We performed simulations to extrapolate the g-factors and coupling constants of the observed components. We carried out pulse annealing experiments to determine the trap depth of the centres originating such signals. The hydrogen related centre signal has been simulated with the g-tensor's main components being g1 = 2.0007, g2 = 1.9974 and g3 = 1.9929, with coupling constants A1 = 233 MHz, A2 = 235 MHz and A3 = 239 MHz, and trap depth of 1.14 eV.