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A study of thermoluminescence emission spectra and optical stimulation spectra of quartz from different provenances
Radiation Measurements 32 (2000) 653±657
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A study of thermoluminescence emission spectra and optical stimulation spectra of quartz from dierent provenances R. Kuhn a,*, T. Trautmann b, A.K. Singhvi a,b,c, M.R. Krbetschek d, G.A. Wagner a, W. Stolz b a
Forschungsstelle ArchaÈometrie der Heidelberger Akademie der Wissenschaften am Max-Planck-Institut fuÈr Kernphysik, P.O. Box 103980, D-69029 Heidelberg, Germany b Institut fuÈr Angewandte Physik, Bergakademie, B.-v.-Cotta-Str. 4, D-09596 Freiberg, Germany c Earth Science Division, Physical Research Laboratory, Ahmedabad, 380 009, India d Saxon Academy of Sciences in Leipzig, B.-v.-Cotta-Str. 4, D-09596 Freiberg, Germany Received 19 October 1999; received in revised form 9 March 2000; accepted 16 March 2000
Abstract The present study examines (1) variability in the thermoluminescence (TL) emission spectrum and optical stimulation (OSL) spectrum of quartz from dierent provenances and, (2) possible correlations between spectral features and the nature of the complex growth curves (ranging from saturating exponential to those described by a cubic polynomial function), so as to determine the validity of the currently used experimental protocols. The results suggest that commonly used UV emission for dating constitutes only a minor component of the total quartz emission and in view of this a dose-dependent contribution from blue/blue±green emission peak to the UV detection is likely. The OSL stimulation spectrum shows a de®nite change in stimulation response between 500±520 nm, hence implying that stimulation in this window may contribute as an additional source of scatter in multi-grain samples. 7 2000 Elsevier Science Ltd. All rights reserved.
1. Introduction Quartz with its ubiquitous nature, resistance to weathering, optical bleaching properties of its thermoluminescence (TL) and optically stimulated luminescence (OSL) with day-light stimulation, high thermal stability and absence of anomalous fading, is an attractive mineral for luminescence dating. Much work on
* Corresponding author. E-mail address: [email protected] (R. Kuhn).
thermoluminescence, optically stimulated luminescence and dosimetric properties of the quartz has been reported (e.g. Krbetschek et al. (1997), Huntley et al., 1991; David et al., 1977). However, a systematic and comparative investigation of TL and OSL properties of quartz from dierent provenances has still not been attempted. In view of the fact that dating protocols developed for age analysis using quartz based on a single provenance are usually applied to quartz from other regions, it was considered desirable to investigate the range and variability of luminescence properties of quartz. In the present paper, a comparative study of
1350-4487/00/$ - see front matter 7 2000 Elsevier Science Ltd. All rights reserved. PII: S 1 3 5 0 - 4 4 8 7 ( 0 0 ) 0 0 0 9 0 - 1
654
R. Kuhn et al. / Radiation Measurements 32 (2000) 653±657
TL emission spectra and OSL spectra of quartz from 13 dierent sites all over the world (Fig. 1) is presented. 2. Experimental details The TL emission spectra were recorded at Freiberg using a spectrometer comprising a Jobin Yvon CP200 spectrograph (200±800 nm) with a liquid nitrogen cooled CCD array (Astromed P88131) and a temperature programmer (heating rate 2 K sÿ1). The TL emission spectra were not corrected for the equipment spectral response that was nearly constant between 800 and 400 nm and had somewhat enhanced sensitivity between 400 and 200 nm with a maximum at 280 nm (Rieser, 1999). No heat rejection ®lter was used to ensure measurements in the region 200±300 nm. Although such ®lters reject long wavelength radiation by de®nition, they may also absorb in the UV range. This however restricted glow curves to 3808C due to the interference from the black body radiation. Measurements of TL/OSL growth curves (TL heating rate 5 K sÿ1) and OSL excitation spectra were made using a standard Risù TL-DA-12 TL/OSL reader and detection window from 300 to 390 nm using a combination of DESAG MUG-2 and HOYA U-340 ®lters. This is because most of the dating work is carried out using the rapidly bleaching UV emission of the 3258C glow peak, (Prescott and Fox, 1990; Schole®eld et al., 1994). Special eort was made to examine the nature of TL growth curves in excess of 250 Gy as anomalous increase in luminescence sensitivities has been reported for some samples (HuÈtt & Smirnov, 1982; Fleming, 1969; Chawla et al., 1998). For the growth curves, all samples were bleached in a SOL-2 sunlight simulator for 2 h. After irradiation and storage of r24 h at 708C, so as to eliminate irradiation
Fig. 1. Location of the sites. The map shows the provenances of samples (dots) used in this study (schematic). One dot may represent more than one sample.
induced phosphorescence, samples were measured, for the TL vs. dose response without any additional preheat. IRSL checks on both natural and dosed samples were performed to ensure that shape and intensities of the dose response curves are not due to bright feldspar inclusions. The OSL spectral measurements were carried out on natural samples using a 150 W Xenon arc lamp attached via a quartz light guide and an OSL ring adapter to the reader (Kuhn, 1993). A set of interference ®lters (Schott DMZ 20-2) combined with heat absorbing (HA3) and edge cut glass ®lters (GG 420) were used to de®ne the stimulation wavelength. This con®guration delivered a mean ¯ux of approximately 2 mW cmÿ2 at the sample position on the heating plate. Spectral intensity changes of the xenon lamp spectrum in the region between 450 nm and 500 nm were cor-
Fig. 2. Dierent types of TL spectra, (a) a dominant orange/ red emission, sample BU3, with the detection window for the TL glowcurve marked as a box in the spectral plot, (b) an orange/red and blue/blue±green emission of comparable intensities, sample OM15B and (c) a dominant blue/blue±green emission, sample TR21.
R. Kuhn et al. / Radiation Measurements 32 (2000) 653±657
655
rected for each interference ®lter by ¯ux measurement at sample position on the heating plate. The OSL stimulation spectra thus was corrected for lamp ¯ux and so for wavelength dependence of the power output of the xenon lamp. The detection optics was de®ned by ®lters MUG-2 and U-340, resulting in a spectral window from 300 to 390 nm. Normalization of the shine-down curves (20 s stimulation) was done using 0.4 s short-shines. Standard preheat of 2208C for 300 s was used. 3. Results Thirteen samples of dierent provenances were analysed for their emission spectrum, glowcurves, growthcurves and OSL stimulation spectrum. Typical TL emission spectra are plotted in Fig. 2. Fig. 3 provides a deconvolution of a TL emission spectrum. TL growth curves for two typical samples are given in Fig. 4 and Fig. 5 provides a typical OSL stimulation spectrum. 4. Discussion Table 1 gives a summary of the TL emission spectra of 13 dierent sites that can be classi®ed in three types: 1. A dominant orange/red emission. 2. Orange/red and blue/blue±green emissions of comparable intensities. 3. A dominant blue/blue±green emission.
Fig. 4. Type-I TL growth curve ®tted at 3258C, saturating exponential, sample: BS1 (top), and (bottom) type-II TL growth curve showing a dose response at 03258C best described with a 3nl order polynomial, sample BU2.
and U-340, transmission from 300 to 390 nm), it is likely that at higher doses this UV signal may have an increasing contribution from the high-energy tail of the
In all the cases the intensity of the UV emission commonly used for dating is <1% compared to the blue/ blue±green emission. In view of the fact that the detection window was de®ned by the ®lters used (MUG-2
Fig. 3. ``Slice plot'' of the TL spectrum of sample MDL12. The ®t of the peaks shown is based on an energy scale and was transformed into wavelength scale.
Fig. 5. OSL excitation spectrum, sample BF2. The integral intensity of a 20 s shine-down (logarithmic values) is plotted against the central wavelength of a given interference ®lter.
656
R. Kuhn et al. / Radiation Measurements 32 (2000) 653±657
blue emission. It would therefore be prudent to use an additional edge cut ®lter that would restrict/eliminate such an interference by the blue emission. The TL glow curves recorded with a photomultiplier tube in the 300±390 nm UV region give additional important information (e.g. number and shape of the glow peaks for the selected detection range at dierent temperatures). With the exception of sample BU2, most samples exhibited a dose response in the UV region that could be described by a saturating exponential ®t (see Fig. 4). This implies that growth curves described by polynomials perhaps arise due to an increasing contribution from the rapidly growing blue/blue±green emission. A similar suggestion has been made recently by Rieser (1999, pers. comm.). However, a systematic dependence on the type of growth curve mentioned above was not seen. The OSL stimulation spectra generally show an
increase in the signal with decreasing stimulation wavelength as reported before by other authors (Bùtter-Jensen et al., 1994; Ditlefsen and Huntley, 1994; Huntley et al., 1991 1996). The stimulation curves exhibit a distinct change of response at approx. 500 nm (02.5 eV respectively) and can be described by two exponentials. The slope of the curves is smaller for wavelengths <500 nm than for wavelengths >500 nm. A simple model with one type of electron trap would lead to a continuous increase of OSL intensity with increasing energy of the stimulating photons. The change in slope at 02.5 eV (500 nm), implies a deviation from the onetrap model. Such a deviation has also been reported by Bùtter-Jensen et al. (1994) for thermally annealled and irradiated quartz. The existence of an absorption band at 02.5 eV was suggested to explain a decreasing rate in OSL response enhancement with higher photon energy. An alternative description for the entire wavelength region through 500 nm would require a physical
Table 1 Sample list of TL spectra measured. Grouping of the spectra is indicated by indices (1dominant orange/ red emission, 2 orange/ red & blue/blue±green emissions of comparable intensities, 3 dominant blue/blue±green emission). The markers give relative intensities of a spectrum at given wavelength regions
R. Kuhn et al. / Radiation Measurements 32 (2000) 653±657
model including two types of charge traps with charge populations and a decrease of recombination centres such that the trap competition eect provides such a response change. This would, however, need modelling. On a more applied aspect, ``change over'' wavelength occurs in the range of 500±520 nm. In this study of OSL stimulation spectra only naturally dosed samples have been measured. As long as it is not proved that arti®cial irradiation with dose-rates that are dierent from the natural dose-rate by a factor of 108±109 produces identical stimulation spectra, caution must be taken to avoid optical stimulation in this wavelength region because of a possible shift of the borderline between higher and smaller slope of the OSL response curve. Stimulation in this region may introduce an additional variability in the dating results. Until this is further examined, it is recommended to use wavelength stimulation bands that are far from this 500±520 nm region. 5. Conclusion The present study indicates that 1. The commonly used UV emission for dating applications constitutes only a minor fraction of the total TL signal. This implies that the higher energy tail of the blue emission may interfere with this emission (especially at higher doses) if the detection optics are not adequately speci®ed. 2. The OSL stimulation spectra show a distinct change in response at the range 500±520 nm. Hence the stimulation in this range is to be avoided to minimize additional scatter in luminescence output from identical samples.
References Bùtter-Jensen, L., Duller, G.A.T., Poolton, N.R.J., 1994. Excitation and emission spectrometry of stimulated lumi-
657
nescence from quartz and feldspars. Radiation Measurements 23, 613±616. Chawla, S., Rao, T.K.G., Singhvi, A.K., 1998. Quartz thermoluminescence: Dose and dose-rate eects and their implications. Radiation Measurements 29 (1), 53±63. David, M., Sunta, C.M., Ganguly, A.K., 1977. Thermoluminescence of quartz. Part 1: Glow curve and spectral characteristics. Indian Journal of Pure and Applied Physics 15, 201±204. Ditlefsen, C., Huntley, D.J., 1994. Optical excitation of trapped charges in quartz, potassium feldspars and mixed silicates: the dependence on photon energy. Radiation Measurements 23, 675±682. Fleming, S. 1969. The acquisition of radioluminescence by ancient ceramics. Unpublished Ph.D. thesis, Faculty of Physical Sciences, Oxford University. HuÈtt, G., Smirnov, A., 1982. Detailed thermoluminescence dating studies of samples from geological reference pro®les in Central Russia. PACT J 6, 505±511. Huntley, D.J., Godfrey-Smith, D.I., Haskell, E.H., 1991. Light-induced emission spectra from some quartz and feldspars. Nucl. Tracks Rad. Meas. 18, 127±131. Huntley, D.J., Short, M.A., Dunphy, K., 1996. Deep traps in quartz and their use for optical dating. Canad. J. Phys. 74, 81±91. Krbetschek, M.R., Goetze, J., Dietrich, A., Trautman, T., 1997. Spectral information from minerals relevant for luminescence dating. Radiation Measurements 27, 695± 748. Kuhn, R. 1993. Aufbau einer Stimulationslichtquelle und erste Untersuchungen des PhaÈnomens der Optisch (GruÈn) Stimulierten Lumineszenz zum Zwecke der Altersbestimmung. Unpublished diploma thesis, Faculty of Physics and Astronomy, University of Heidelberg. Prescott, J.R., Fox, P.J., 1990. Dating quartz sediments using the 3258C TL peak; new spectral data. Ancient TL 8, 32± 34. Rieser, U., 1999. Spectrometric investigations of feldspars as a contribution towards understanding of the physical basis of the luminescence dating technique. Dissertation, Combined Faculties for the Natural Sciences and for Mathematics, University of Heidelberg. Schole®eld, R.B., Prescott, J.R., Franklin, A.D., Fox, P.J., 1994. Observations on some thermoluminescence emission centres in geological quartz. Radiation Measurements 23 (2/3), 409±412.
www.elsevier.com/locate/radmeas
A study of thermoluminescence emission spectra and optical stimulation spectra of quartz from dierent provenances R. Kuhn a,*, T. Trautmann b, A.K. Singhvi a,b,c, M.R. Krbetschek d, G.A. Wagner a, W. Stolz b a
Forschungsstelle ArchaÈometrie der Heidelberger Akademie der Wissenschaften am Max-Planck-Institut fuÈr Kernphysik, P.O. Box 103980, D-69029 Heidelberg, Germany b Institut fuÈr Angewandte Physik, Bergakademie, B.-v.-Cotta-Str. 4, D-09596 Freiberg, Germany c Earth Science Division, Physical Research Laboratory, Ahmedabad, 380 009, India d Saxon Academy of Sciences in Leipzig, B.-v.-Cotta-Str. 4, D-09596 Freiberg, Germany Received 19 October 1999; received in revised form 9 March 2000; accepted 16 March 2000
Abstract The present study examines (1) variability in the thermoluminescence (TL) emission spectrum and optical stimulation (OSL) spectrum of quartz from dierent provenances and, (2) possible correlations between spectral features and the nature of the complex growth curves (ranging from saturating exponential to those described by a cubic polynomial function), so as to determine the validity of the currently used experimental protocols. The results suggest that commonly used UV emission for dating constitutes only a minor component of the total quartz emission and in view of this a dose-dependent contribution from blue/blue±green emission peak to the UV detection is likely. The OSL stimulation spectrum shows a de®nite change in stimulation response between 500±520 nm, hence implying that stimulation in this window may contribute as an additional source of scatter in multi-grain samples. 7 2000 Elsevier Science Ltd. All rights reserved.
1. Introduction Quartz with its ubiquitous nature, resistance to weathering, optical bleaching properties of its thermoluminescence (TL) and optically stimulated luminescence (OSL) with day-light stimulation, high thermal stability and absence of anomalous fading, is an attractive mineral for luminescence dating. Much work on
* Corresponding author. E-mail address: [email protected] (R. Kuhn).
thermoluminescence, optically stimulated luminescence and dosimetric properties of the quartz has been reported (e.g. Krbetschek et al. (1997), Huntley et al., 1991; David et al., 1977). However, a systematic and comparative investigation of TL and OSL properties of quartz from dierent provenances has still not been attempted. In view of the fact that dating protocols developed for age analysis using quartz based on a single provenance are usually applied to quartz from other regions, it was considered desirable to investigate the range and variability of luminescence properties of quartz. In the present paper, a comparative study of
1350-4487/00/$ - see front matter 7 2000 Elsevier Science Ltd. All rights reserved. PII: S 1 3 5 0 - 4 4 8 7 ( 0 0 ) 0 0 0 9 0 - 1
654
R. Kuhn et al. / Radiation Measurements 32 (2000) 653±657
TL emission spectra and OSL spectra of quartz from 13 dierent sites all over the world (Fig. 1) is presented. 2. Experimental details The TL emission spectra were recorded at Freiberg using a spectrometer comprising a Jobin Yvon CP200 spectrograph (200±800 nm) with a liquid nitrogen cooled CCD array (Astromed P88131) and a temperature programmer (heating rate 2 K sÿ1). The TL emission spectra were not corrected for the equipment spectral response that was nearly constant between 800 and 400 nm and had somewhat enhanced sensitivity between 400 and 200 nm with a maximum at 280 nm (Rieser, 1999). No heat rejection ®lter was used to ensure measurements in the region 200±300 nm. Although such ®lters reject long wavelength radiation by de®nition, they may also absorb in the UV range. This however restricted glow curves to 3808C due to the interference from the black body radiation. Measurements of TL/OSL growth curves (TL heating rate 5 K sÿ1) and OSL excitation spectra were made using a standard Risù TL-DA-12 TL/OSL reader and detection window from 300 to 390 nm using a combination of DESAG MUG-2 and HOYA U-340 ®lters. This is because most of the dating work is carried out using the rapidly bleaching UV emission of the 3258C glow peak, (Prescott and Fox, 1990; Schole®eld et al., 1994). Special eort was made to examine the nature of TL growth curves in excess of 250 Gy as anomalous increase in luminescence sensitivities has been reported for some samples (HuÈtt & Smirnov, 1982; Fleming, 1969; Chawla et al., 1998). For the growth curves, all samples were bleached in a SOL-2 sunlight simulator for 2 h. After irradiation and storage of r24 h at 708C, so as to eliminate irradiation
Fig. 1. Location of the sites. The map shows the provenances of samples (dots) used in this study (schematic). One dot may represent more than one sample.
induced phosphorescence, samples were measured, for the TL vs. dose response without any additional preheat. IRSL checks on both natural and dosed samples were performed to ensure that shape and intensities of the dose response curves are not due to bright feldspar inclusions. The OSL spectral measurements were carried out on natural samples using a 150 W Xenon arc lamp attached via a quartz light guide and an OSL ring adapter to the reader (Kuhn, 1993). A set of interference ®lters (Schott DMZ 20-2) combined with heat absorbing (HA3) and edge cut glass ®lters (GG 420) were used to de®ne the stimulation wavelength. This con®guration delivered a mean ¯ux of approximately 2 mW cmÿ2 at the sample position on the heating plate. Spectral intensity changes of the xenon lamp spectrum in the region between 450 nm and 500 nm were cor-
Fig. 2. Dierent types of TL spectra, (a) a dominant orange/ red emission, sample BU3, with the detection window for the TL glowcurve marked as a box in the spectral plot, (b) an orange/red and blue/blue±green emission of comparable intensities, sample OM15B and (c) a dominant blue/blue±green emission, sample TR21.
R. Kuhn et al. / Radiation Measurements 32 (2000) 653±657
655
rected for each interference ®lter by ¯ux measurement at sample position on the heating plate. The OSL stimulation spectra thus was corrected for lamp ¯ux and so for wavelength dependence of the power output of the xenon lamp. The detection optics was de®ned by ®lters MUG-2 and U-340, resulting in a spectral window from 300 to 390 nm. Normalization of the shine-down curves (20 s stimulation) was done using 0.4 s short-shines. Standard preheat of 2208C for 300 s was used. 3. Results Thirteen samples of dierent provenances were analysed for their emission spectrum, glowcurves, growthcurves and OSL stimulation spectrum. Typical TL emission spectra are plotted in Fig. 2. Fig. 3 provides a deconvolution of a TL emission spectrum. TL growth curves for two typical samples are given in Fig. 4 and Fig. 5 provides a typical OSL stimulation spectrum. 4. Discussion Table 1 gives a summary of the TL emission spectra of 13 dierent sites that can be classi®ed in three types: 1. A dominant orange/red emission. 2. Orange/red and blue/blue±green emissions of comparable intensities. 3. A dominant blue/blue±green emission.
Fig. 4. Type-I TL growth curve ®tted at 3258C, saturating exponential, sample: BS1 (top), and (bottom) type-II TL growth curve showing a dose response at 03258C best described with a 3nl order polynomial, sample BU2.
and U-340, transmission from 300 to 390 nm), it is likely that at higher doses this UV signal may have an increasing contribution from the high-energy tail of the
In all the cases the intensity of the UV emission commonly used for dating is <1% compared to the blue/ blue±green emission. In view of the fact that the detection window was de®ned by the ®lters used (MUG-2
Fig. 3. ``Slice plot'' of the TL spectrum of sample MDL12. The ®t of the peaks shown is based on an energy scale and was transformed into wavelength scale.
Fig. 5. OSL excitation spectrum, sample BF2. The integral intensity of a 20 s shine-down (logarithmic values) is plotted against the central wavelength of a given interference ®lter.
656
R. Kuhn et al. / Radiation Measurements 32 (2000) 653±657
blue emission. It would therefore be prudent to use an additional edge cut ®lter that would restrict/eliminate such an interference by the blue emission. The TL glow curves recorded with a photomultiplier tube in the 300±390 nm UV region give additional important information (e.g. number and shape of the glow peaks for the selected detection range at dierent temperatures). With the exception of sample BU2, most samples exhibited a dose response in the UV region that could be described by a saturating exponential ®t (see Fig. 4). This implies that growth curves described by polynomials perhaps arise due to an increasing contribution from the rapidly growing blue/blue±green emission. A similar suggestion has been made recently by Rieser (1999, pers. comm.). However, a systematic dependence on the type of growth curve mentioned above was not seen. The OSL stimulation spectra generally show an
increase in the signal with decreasing stimulation wavelength as reported before by other authors (Bùtter-Jensen et al., 1994; Ditlefsen and Huntley, 1994; Huntley et al., 1991 1996). The stimulation curves exhibit a distinct change of response at approx. 500 nm (02.5 eV respectively) and can be described by two exponentials. The slope of the curves is smaller for wavelengths <500 nm than for wavelengths >500 nm. A simple model with one type of electron trap would lead to a continuous increase of OSL intensity with increasing energy of the stimulating photons. The change in slope at 02.5 eV (500 nm), implies a deviation from the onetrap model. Such a deviation has also been reported by Bùtter-Jensen et al. (1994) for thermally annealled and irradiated quartz. The existence of an absorption band at 02.5 eV was suggested to explain a decreasing rate in OSL response enhancement with higher photon energy. An alternative description for the entire wavelength region through 500 nm would require a physical
Table 1 Sample list of TL spectra measured. Grouping of the spectra is indicated by indices (1dominant orange/ red emission, 2 orange/ red & blue/blue±green emissions of comparable intensities, 3 dominant blue/blue±green emission). The markers give relative intensities of a spectrum at given wavelength regions
R. Kuhn et al. / Radiation Measurements 32 (2000) 653±657
model including two types of charge traps with charge populations and a decrease of recombination centres such that the trap competition eect provides such a response change. This would, however, need modelling. On a more applied aspect, ``change over'' wavelength occurs in the range of 500±520 nm. In this study of OSL stimulation spectra only naturally dosed samples have been measured. As long as it is not proved that arti®cial irradiation with dose-rates that are dierent from the natural dose-rate by a factor of 108±109 produces identical stimulation spectra, caution must be taken to avoid optical stimulation in this wavelength region because of a possible shift of the borderline between higher and smaller slope of the OSL response curve. Stimulation in this region may introduce an additional variability in the dating results. Until this is further examined, it is recommended to use wavelength stimulation bands that are far from this 500±520 nm region. 5. Conclusion The present study indicates that 1. The commonly used UV emission for dating applications constitutes only a minor fraction of the total TL signal. This implies that the higher energy tail of the blue emission may interfere with this emission (especially at higher doses) if the detection optics are not adequately speci®ed. 2. The OSL stimulation spectra show a distinct change in response at the range 500±520 nm. Hence the stimulation in this range is to be avoided to minimize additional scatter in luminescence output from identical samples.
References Bùtter-Jensen, L., Duller, G.A.T., Poolton, N.R.J., 1994. Excitation and emission spectrometry of stimulated lumi-
657
nescence from quartz and feldspars. Radiation Measurements 23, 613±616. Chawla, S., Rao, T.K.G., Singhvi, A.K., 1998. Quartz thermoluminescence: Dose and dose-rate eects and their implications. Radiation Measurements 29 (1), 53±63. David, M., Sunta, C.M., Ganguly, A.K., 1977. Thermoluminescence of quartz. Part 1: Glow curve and spectral characteristics. Indian Journal of Pure and Applied Physics 15, 201±204. Ditlefsen, C., Huntley, D.J., 1994. Optical excitation of trapped charges in quartz, potassium feldspars and mixed silicates: the dependence on photon energy. Radiation Measurements 23, 675±682. Fleming, S. 1969. The acquisition of radioluminescence by ancient ceramics. Unpublished Ph.D. thesis, Faculty of Physical Sciences, Oxford University. HuÈtt, G., Smirnov, A., 1982. Detailed thermoluminescence dating studies of samples from geological reference pro®les in Central Russia. PACT J 6, 505±511. Huntley, D.J., Godfrey-Smith, D.I., Haskell, E.H., 1991. Light-induced emission spectra from some quartz and feldspars. Nucl. Tracks Rad. Meas. 18, 127±131. Huntley, D.J., Short, M.A., Dunphy, K., 1996. Deep traps in quartz and their use for optical dating. Canad. J. Phys. 74, 81±91. Krbetschek, M.R., Goetze, J., Dietrich, A., Trautman, T., 1997. Spectral information from minerals relevant for luminescence dating. Radiation Measurements 27, 695± 748. Kuhn, R. 1993. Aufbau einer Stimulationslichtquelle und erste Untersuchungen des PhaÈnomens der Optisch (GruÈn) Stimulierten Lumineszenz zum Zwecke der Altersbestimmung. Unpublished diploma thesis, Faculty of Physics and Astronomy, University of Heidelberg. Prescott, J.R., Fox, P.J., 1990. Dating quartz sediments using the 3258C TL peak; new spectral data. Ancient TL 8, 32± 34. Rieser, U., 1999. Spectrometric investigations of feldspars as a contribution towards understanding of the physical basis of the luminescence dating technique. Dissertation, Combined Faculties for the Natural Sciences and for Mathematics, University of Heidelberg. Schole®eld, R.B., Prescott, J.R., Franklin, A.D., Fox, P.J., 1994. Observations on some thermoluminescence emission centres in geological quartz. Radiation Measurements 23 (2/3), 409±412.