Electron spin resonance dating and dosimetry of tooth enamel

• Main Author: Jonas, M.
• Published: University of Cambridge 1997
• Subjects: 560
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.605678

Electron spin resonance (ESR) dating is an absolute dating method suitable for the Quaternary (up to 2 million years for tooth enamel). It is based on determining the natural radiation dose to which a sample has been exposed during its burial period. Two methods of deconvolution of ESR spectra are demonstrated. It is argued that the use of integrated spectra is most suitable for dating and dosimetry. This method is applied to the ESR dating signal in fossil tooth enamel. Initially, two models is given consistent results. A broad underlying isotropic signal at <I>g</I>=2.007 is found regardless of the model applied. Q-band ESR spectra of fossil tooth enamel are consistent with a model that describes the spectrum as a superposition of an axialsymmetrically split signal and two isotropic signals. A narrow additional signal is also observed which may interfere with dose response curves. ESR spectra of unirradiated and irradiated aliquots of five samples of Quaternary enamel have been deconvoluted, and growth curves have been generated for each signal component. A model is presented that describes the radiation response of a polycrystalline material. The assumptions underlying the model, the resulting differential equations and a numerical method by which they an be resolved are presented. The model parameters and their correlation with real-world parameters are discussed. The properties of the model and the scope of calculations that can be performed are demonstrated. Tooth enamel has been irradiated in a white synchrotron radiation beam and saturation of the spin concentration has been observed. An absolute spin concentration at saturation of about 3x10<SUP>17</SUP> spins/cm<SUP>3</SUP> for each of the signal components has been found. The directly measured values agree with saturation concentrations determined by extrapolation from fossil tooth enamel. These results support the possibility of a universal growth curve for tooth enamel.