Charge recombination processes in minerals studied using optically stimulated luminescence and time-resolved exo-electrons

Sumiko Tsukamoto (1, 2, 3) , Andrew Murray (2) , Christina Ankjaergaard (3) , Mayank Jain (3) , Torben Lapp (3)

1 LIAG - Leibniz Institute for Applied Geophysics
2 Department of Earth Sciences [Aarhus]
3 Risø DTU - Risø National Laboratory for Sustainable Energy

A time-resolved optically stimulated exo-electron (TR-OSE) measurement system has been developed using a Photon Timer attached to a gas-flow semi-proportional pancake electron detector within a Risø TL/OSL reader. The decay rate of the exo-electron emission after the stimulation pulse depends on the probability of (1) escape of electrons into the detector gas from the conduction band by overcoming the work function of the material, and (2) thermalisation of electrons in the conduction band, and subsequent re-trapping/recombination. Thus we expect the exo-electron signal to reflect the instantaneous electron concentration in the conduction band. In this study, TR-OSE and TR-OSL were measured for the first time using quartz, K-feldspar and NaCl by stimulating the samples using pulsed blue LEDs at different temperatures between 50 and 250 °C after beta irradiation and preheating to 280 °C. The majority of TR-OSE signals from all the samples decayed much faster than TR-OSL signals irrespective of the stimulation temperatures. This suggests that the lifetime of OSL in these dosimeters arises mainly from the relaxation of an excited state of the recombination centre, rather than from residence time of an electron in the conduction band.

Mots clés: optically stimulated; time-resolved; luminescence; lifetime; exo-electron; quartz; feldspar; NaCl 2

Sumiko Tsukamoto, Andrew Murray, Christina Ankjaergaard, Mayank Jain, Torben Lapp. Charge recombination processes in minerals studied using optically stimulated luminescence and time-resolved exo-electrons. Journal of Physics D: Applied Physics, 2010, 43 (32), pp.325502. ⟨10.1088/0022-3727/43/32/325502⟩. ⟨hal-00569672⟩