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X- and Q-band electron paramagnetic resonance of CO2- in hydroxyapatite single crystals
G C Vanhaelewyn1, R A Morent, F J Callens
1Laboratory for Crystallography and Study of the Solid State, Ghent University, Krijgslaan 281-S1, B-9000 Gent, Belgium.
Abstract:
Both X- and Q-band electron paramagnetic resonance (EPR) research has been conducted using slightly carbonated hydroxyapatite (HAp) single crystals after exposure to ionizing radiation. Below a temperature of 90 K, O(-) and CO(2-) radicals were detected, whereas at room temperature only CO(2-) spectra could be observed. The O(-) ion has previously been investigated in high-purity HAp single crystals, whereas EPR spectra of CO(2-) in HAp single crystals have not been reported. Both paramagnetic defects exhibit EPR angular variations in planes containing the c axis of the crystal from which spin Hamiltonian parameters were derived. Arguments are given for the presence of two CO(2-) defects in the irradiated HAp single crystals.