An analytical model for the growth of ESR signals (original) (raw)
Related papers
Dose-response and thermal behaviour of the esr signal at g = 2.0006 in carbonates
Quaternary Science Reviews, 1992
Growth curves of the ESR dating signal at g = 2.0006 on irradiation have been carefully examined. They revealed that a description by a single exponential saturation function is only a good approximation in the dose range smaller than 1 kGy. In this dose range the saturation dose, Do, for carbonates was found to be between 400 and 800 Gy. The systematic deviations from this function and statistical uncertainties limit the reliable AD range to about 250 Gy. Expanded functions and models that explain the observed deviations are given.
An investigation of ESR signals and their related TL emission in speleothem calcite
International Journal of Radiation Applications and Instrumentation. Part A. Applied Radiation and Isotopes, 1989
TL emission spectra were recorded using a sensitive Fourier transform spectrometer for 4 samples of speleothem calcite which had been selected to display a range of ESR signals. Two samples showed principal emissions at 610 nm for both the 160°C and 270°C TL peaks which are attributed to Mn-related luminescence centres, while the remaining two samples had their principal emissions at 480 and 580 nm, which is characteristic of Dy-related luminescence centres. The relative intensities of the TL emission and ESR signals within individual samples, and between those having the same luminescence centres, together with kinetic studies infer correlations between the g = 2.0036 ESR signal and TL emission at 220°C, and the 160~C TL peak and the g = 1.9975 ESR signal. The g-2.0005 signal used for dating appears to correspond with the 270°C TL peak, but at elevated temperatures the mean life of the latter is significantly less than that of the ESR signal. This could be explained if the luminescence centres have a lower stability than the trap sites measured directly by ESR. All correlations should be treated with caution because charge may be lost from ESR traps via different routes in each calcite, giving wide variations in luminescence efficiency.
ESR in the 21st century: From buried valleys and deserts to the deep ocean and tectonic uplift
Earth-Science Reviews, 2016
Electron spin resonance (ESR) dating can date many materials, including hydroxyapatite in enamel and some fish scales, aragonite and calcite in corals, molluscs, some travertine and calcrete, and quartz from ash, fluvial deposits, and some flint. Dating studies using these materials have numerous potential applications in many varied Quaternary settings. ESR dating uses signals resulting from trapped charges created by radiation in crystalline solids. Ages are calculated by comparing the accumulated radiation dose in the dating sample with the internal and external radiation dose rates produced by natural radiation in and around the sample and produced by cosmic radiation. When compared to other dating techniques, age agreement has been excellent for teeth, corals, molluscs, and quartz. Recent improvements have included using a more complex modelling technique to calculate the cosmic dose rates and more detailed modelling techniques for dealing with variable external dose rates. Methods in development include using quartz from buried fluvial valleys to date geomorphic surfaces and using the signals in barnacles and benthic foraminifera for dating fossils or their associated sediment. New chronometer applications recently developed include using coral and mollusc dates to build sealevel curves and to monitor volcanic activity and tectonic uplift, using tooth and mollusc dates to assess water availability in deserts, and using isochron data to assess U uptake processes into teeth. When coupled with other geochemical and geomorphological techniques, ESR can provide the chronometric control to build paleoclimatic and other paleoenvironmental records. Many other applications are possible, from heating studies for artefacts to dating sulphates and other minerals on distant planets.
ESR EXPERIMENTS ON QUATERNARY CALCITES AND BONES FOR DATING PURPOSES
A series of experiments and measurements regarding sample preparation, peak intensity estimation, annealing, signal identification, dose determination and dose-rate estimation were carried out in order to explore the technique of ESR for dating speleothemes and bones. In addition, for the first time, the behaviour of peaks at low temperatures (room temperature to 4K) has been studied. Materials from the cave Apidima in Peloponnese, where anthropological remains were discovered, have been used for this study. The results indicate the ~xistenee of four peaks, two organic and two radiation induced. Their intensity is increased at 260K and therefore the sensitivity of the technique is enhanced at lower temperatures. The bone samples were found to have absorbed large amounts of uranium from the environment making their dating impossible. A range of ages 20-45 9 103 years have been calculated for the travertines of the cave, taking into account all possible factors affecting the age.
Basic ESR studies on recent corals
Quaternary Science Reviews, 1992
Experiments on recent corals (Acropora palmata, Barbados) were carried out to study the dating relevant properties of the characteristic ESR signals. Highly resolved signal growth curves (55 aliquots of a sieve fraction 125-250 ~tm) were obtained by y-irradiation in small steps up to 20 kGy. The signal growth curve of the "dating signal" at g = 2.0006 can only he approximated by a single exponential saturation function in a certain dose range. Thus, ADs derived with this function tend to be overestimated. A better analytical description by two different functions was tested. Isothermal annealing experiments were carried out at various temperatures before and after irradiation with a definite y-dose respectively. The thermal decay of the dating signal is not 1st order. Furthermore, the decay process is strongly influenced by the decay of the traps themselves. The behaviour of the signals at g = 2.0057 and g = 2.0031 was compared with that of the dating signal. A surprising result was the growth of the signal at g = 2.0057 with y-irradiation.
Radiation Measurements, 1998
ÐA modern red deer bone was heated in a mue furnace at increasing temperatures in the range 200 to 9408C. Samples were analyzed by infrared and X-ray diraction spectrometry before measurement of the ESR signals around g = 2.002 by ESR spectrometry. Each sample was irradiated by a gamma source (cobalt-60) at increasing doses in the range 100 to 10 000 Gy. g-irradiated samples were then analyzed by ESR spectrometry in order to obtain the growth curve and to show ESR signal behavior. ESR signals of fossil bones from archaeological deposits of the Lazaret cave (Middle Pleistocene, France) were studied and colors were compared with modern samples in order to assess at which temperature these fossil bones were heated in prehistoric ®replaces.
Quaternary Geochronology, 2015
Luminescence and ESR dating methods of quartz sediment are based on the natural resetting of the signal by light exposure (optical bleaching). When the bleaching is incomplete, a residual dose (Dr) is added to the post-depositional dose accumulated since the deposit and hence the age is overestimated. Insufficient bleaching is usually linked to the environment and conditions of transport/deposition of the quartz grains affecting the light exposure duration. Indeed, each transportation mode-fluvial, marine or aeolian e is associated to specific conditions of light exposure, depending mainly to the location of grains in the transport agent during the transport phase, the opacity of the transport environment and the velocity of the transport. The present study attempts to discriminate the modes of transport/deposition providing a satisfying reset of the ESR signals of quartz grains. For this purpose, we investigated bleaching rates and ESR residual doses of aluminum centers from “present-day” aeolian, fluvial and marine sediments sampled in various sedimentary environments. The bleaching efficiency evaluation in these different environments may help for a better understanding of the resetting phenomenon for quartz signals which represents presently the main difficulty for ESR dating. The results show that the residual doses are small enough to allow an ESR dating of the main part of the sediment transported in almost all the context examined in this study. The smallest residual doses are obtained from quartz grains within the range of 100-200 mm and transported in clear water. Some limits for the application of optically bleached quartz ESR dating appears nevertheless, mainly when the residual dose and the dose accumulated after the deposit are quite similar, i.e. for Upper Pleistocene samples.
Acta Physica Polonica A - ACTA PHYS POL A, 2006
Natural calcite samples were collected from the dripstone layers of the Black Cave of the Tatra Mountains. ESR spectra, thermal analysis, and thermoluminescence data were analysed to obtain a consistent picture of the calcite properties. The ESR spectra were analysed using computer enhanced resolution spectra and an influence of the thermal annealing on intensity of individual ESR lines was measured. These results together with the effects of gamma-irradiation in ESR spectra allowed one to discriminate between ESR lines from various paramagnetic centres. A general conclusion of the paper is that in the ESR dating the outer ESR lines of CO-3 (g=2.0125) and CO-2 (g=1.9980) radicals should be used instead of the commonly used multicomponent central line.