The slow component of quartz optically stimulated
luminescence
R.M. Bailey
Oxford Luminescence Research Group, Research Laboratory for Archaeology and the History of Art, University of Oxford, Oxford
OX1 3QJ, UK
Received 13 May 1999; received in revised form 6 December 1999; accepted 9 December 1999
Abstract
The slow component of quartz OSL displays a number of properties that clearly distinguish it from the main
(`rapidly bleachable') part of the quartz OSL signal traditionally used for dating. These properties include an
extremely high thermal stability, dose saturation level and a charge concentration dependence in both signal form
and decay rate. The physical mechanism responsible for the slow component is thought at present to involve a
direct donor±acceptor recombination component, possibly associated with competing pathways below, and possibly
up to, the conduction band. The thermal stability and high dose saturation characteristics of the slow component
suggest much potential for long-range dating exists although at present it is uncertain whether diculties associated
with partial resetting may preclude routine use of the slow component for dating sedimentary deposits. A single-
aliquot additive dose method was however used to obtain an estimate of D
e
from the slow component for an
Egyptian quartz sample that was in broad agreement with previous estimates based on the standard multiple-aliquot
additive dose method.
The slow component is often small in magnitude compared to the initial portion of the quartz OSL decay.
However, this is not always the case and for some samples signi®cant inaccuracies in D
e
estimation may occur when
deriving ages from the initial `rapidly bleaching' portion of the OSL decay if the eect of the slow component is
ignored or taken to be constant. 7 2000 Elsevier Science Ltd. All rights reserved.
Keywords: Quartz; Luminescence; Dating; Mechanism; Old
1. Background
The `slow component' refers to a relatively slowly
depleting portion of the quartz optically stimulated
luminescence (OSL) decay, distinct from the main
`rapidly bleached' portion of the signal traditionally
used for optical dating, and was ®rst documented by
Smith in 1989 and by Aitken et al., also in
1989Further observations of the slow component were
reported by Smith and Rhodes in 1994 and more
recently by Bailey et al. (1997) and Bailey (1998). This
paper is a summary of the empirical data obtained so
far from a series of experiments aimed both at under-
standing the physical nature of the slow component
and assessing its potential for obtaining reliable lumi-
nescence dates.
Radiation Measurements 32 (2000) 233±246
1350-4487/00/$ - see front matter 7 2000 Elsevier Science Ltd. All rights reserved.
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E-mail address: richard.bailey@rlaha.ox.ac.uk (R.M. Bai-
ley).