Decomposition of the laboratory gamma irradiation component of angular ESR spectra of fossil tooth enamel fragments

Renaud Joannes-Boyau, Rainer Grun and Thomas Bodin

Abstract

Spectrum decomposition of the angular measurements of fossil tooth enamel fragments using an automated simulated annealing (SA) procedure shows that the mix CO-2 radicals generated by laboratory irradiation is significantly different to that of the natural sample. The naturally irradiated sample contains about 10% of non-oriented CO!2 radicals and a mix of 35:65 orthorhombic to axial CO-2 radicals. In contrast, laboratory irradiation generated about 40% of non-oriented radicals and a large amount of orthorhombic CO-2 radicals, while we failed to detect any axial CO-2 radicals. The results indicate that geological aging of the sample incurs various annealing and transfer processes; their precise nature is yet unknown. Nevertheless, the understanding of the formation and transfer processes that leads to the observed mix of CO-2 radicals in fossil tooth enamel is essential for the reliable application of ESR dating.

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