Luminescence of non-bridging oxygen hole centers as a marker of particle irradiation of α-quartz

Abstract

The origin of the “red” emission bands in the 600 nm–700 nm region, observed in quartz crystals used for luminescence dating and environmental dosimetry, is still controversial. Their reported spectral and lifetime characteristics are often similar to those of oxygen dangling bonds (“non-bridging oxygen hole centers, NBOHCs”) in glassy silicon dioxide. The presence of these “surface radical type” centers in quartz crystal requires sites with highly disordered local structure forming nano-voids characteristic to the structure of glassy SiO2. Such sites are introduced in the tracks of nuclear particles (α-irradiation, neutrons, ions). In case of electrons they are created only at large doses (>5 GGy), approaching amorphization threshold. This study reports a comparison of NBOHC photoluminescence in synthetic quartz and silica glass irradiated by neutrons or 2.5 MeV electrons, and suggests that the red NBOHC photoluminescence band in quartz may serve as a selective marker of an exposure to particle irradiation. It can be distinguished from other red-region luminescence bands by lifetimes in 5–25 μs range, characteristic vibrational structures in the low-temperature spectra and presence of resonance excitation band at ~620 nm.