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Radiation Defects in Lime Mortars and Plasters Studied by EPR Spectroscopy
Published online by Cambridge University Press: 22 June 2020
Abstract
Electron paramagnetic resonance (EPR) spectroscopy is a well-established method of dating based on trapped charges, applied to various crystalline materials, including carbonates, bones, and teeth. It provides a detailed insight into the structure of radiation defects—paramagnetic centers generated by irradiation, without the need of a painstaking sample preparation, often challenging in other methods. Using EPR we studied the effect of γ radiation on lime mortars and plasters from ancient settlement Hippos in Israel, in order to analyze the process of defect generation. Analysis of the complex spectra revealed the presence of radiation-induced species, including CO2–, NO32– and organic radical. Using an artificial UV source, we generated relatively strong signals of paramagnetic centers, analogous to those created by γ irradiation, reaching their maximum intensity after 5–6 hr of UV exposure. Our results confirm the previous reports that radiation defects can also be generated, instead of bleached, in calcite by UV radiation, which is crucial for identifying the issues related to light exposition, affecting the accuracy of age determinations in trapped-charge dating methods.
- Type
- Research Article
- Information
- Radiocarbon , Volume 62 , Issue 3: MoDIM 2018 Proceedings of the Mortar Dating International Meeting , June 2020 , pp. 713 - 724
- Copyright
- © 2020 by the Arizona Board of Regents on behalf of the University of Arizona
Footnotes
Selected Papers from the Mortar Dating International Meeting, Pessac, France, 25–27 Oct. 2018