X- and Q-band electron paramagnetic resonance of CO2- in hydroxyapatite single crystals

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 CO2- radicals were detected, whereas at room temperature only CO2- spectra could be observed. The O- ion has previously been investigated in high-purity HAp single crystals, whereas EPR spectra of CO2- 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 CO2- defects in the irradiated HAp single crystals. (C) 2000 by Radiation Research Society.