language: en

[Confidential: not for distribution. Submitted to IOP Publishing for peer review]

28 April 2010

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

C. Ankjaergaard * , M. Jain
Radiation Research Division, Risø National Laboratory for Sustainable Energy Technical University of Denmark,
DK-4000 Roskilde, Denmark.

[*Corresponding author;]

email: christina.ankjaergaard@gmail.com; Telephone: +45 4677 4920

ABSTRACT Time-resolved OSL curves from quartz are usually measured over a few hundred ¬µs because this time range best illustrates the main component in quartz which lies in the range of 30-45 ¬µs. In this study we present the decay form of quartz time-resolved optically stimulated luminescence (TR-OSL) and optically stimulated phosphorescence (OSP) covering over 8 orders of magnitude from 50 ns to ~8 s. A detailed characterisation of the previously unstudied slowly decaying signals (ms-s 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 4 energy levels. The physical interpretation of the kinetic rate equations is discussed in terms a three trap – one centre model or a one trap – two centres model involving localised charge transfer.

KEYWORDS Quartz, Optically Stimulated Luminescence (OSL), Time-Resolved OSL (TR-OSL), Optically Stimulated Phosphorescence (OSP), Delayed OSL (DOSL), Photo-Transferred Thermoluminescence (PTTL), 110 o C TL trap, kinetic model 1. INTRODUCTION