Decomposition of the angular ESR spectra of fossil tooth enamel fragments

The ESR spectra of a fragment of fossil tooth enamel were measured by rotating it in 10 increments over 360 around its three major axes. We used an automated simulated annealing (SA) procedure for the mathematical decomposition of the spectra. The SA approach is particularly robust in finding global solutions rather than getting stuck in local minima. All angular measurements could be fitted with four Gaussian lines, all of which could be attributed to components of CO2 radicals. The results imply that the tooth enamel fragment contains at least two different types of oriented CO2 radicals, plus about 9% of non-oriented CO2 radicals. The oriented components were tentatively attributed to axial and orthorhombic CO2 radicals. Their explicit locations in the crystal domains of the tooth enamel remain unresolved. 2010 Elsevier Ltd. All rights reserved.