Optically stimulated phosphorescence in quartz over the millisecond to second time scale: insights into the role of shallow traps in delaying luminescent recombination

Time-resolved optically stimulated luminescence (TR-OSL) curves from quartz are usually measured over a few hundred microseconds because this time range best illustrates the main component in quartz which lies in the range 30–45 µs. In this study we present the decay form of quartz TR-OSL and optically stimulated phosphorescence (OSP) covering over 8 orders of magnitude from 50 ns to ~8 s. A detailed characterization of the previously unstudied slowly decaying signals (millisecond–second time scales) is undertaken to understand the origin of these components and the role of re-trapping following optical stimulation. We present preheat and stimulation temperature dependence for both the TR-OSL and OSP curves in these time ranges and use the latter data to determine the E and s values for the participating shallow traps. We observe an abnormal decay behaviour seen as a sudden increase in the decay rate (a 'kink') conspicuous at about 2–3 s in the OSP curves measured at 75 and 100 °C. We satisfactorily reproduce this behaviour with a numerically solved kinetic model consisting of four energy levels. The physical interpretation of the kinetic rate equations is discussed in terms of a three trap–one centre model or a one trap–two centres model involving localized charge transfer.