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

Spectrum decomposition of the angular measurements of fossil tooth enamel fragments using an automated simulated annealing (SA) procedure shows that the mix CO2- radicals generated by laboratory irradiation is significantly different to that of the natural sample. The naturally irradiated sample contains about 10% of non-oriented CO2- radicals and a mix of 35:65 orthorhombic to axial CO2- radicals. In contrast, laboratory irradiation generated about 40% of non-oriented radicals and a large amount of orthorhombic CO2- radicals, while we failed to detect any axial CO2- 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 CO2- radicals in fossil tooth enamel is essential for the reliable application of ESR dating.