EPR OF CARBONATE DERIVED RADICALS - APPLICATIONS IN DOSIMETRY, DATINGAND DETECTION OF IRRADIATED FOOD

After exposure of biological (tooth enamel, bone,...) and synthetic ap atites to ionizing radiation, the so-called ''asymmetric EPR signal ne ar g = 2'' is formed. Although this signal is being used in EPR dosime try, dating and detection of irradiated food for many years already, i ts composite character and the precise nature of the radicals contribu ting to the spectrum are still insufficiently known and/or recognized. For some fifteen years already, the EPR group in Ghent is gaining ext ensive experience on the radicals present in calcified tissues and mod el systems like synthetic apatites, calcites and single crystals doped with carbonate. It will be shown that the majority of radicals in cal cified tissues are carbonate derived, e.g., CO2-, CO3-, CO33- while al so phosphate derived radicals like PO42- and oxygen species (O-, O-3(- )) have been identified with EPR and/or ENDOR. For the EPR application s mentioned above, the most important type of radicals is CO2- (g valu es ranging from 2.0035 to 1.9970). A second type of radicals which is very intriguing but still badly known, exhibits a spectrum at g values around 2.0045. It is very apparent in tooth enamel below doses of 1 G y, it has been observed in certain fossil teeth in a very prominent wa y and also in irradiated food containing bone (e.g., frog legs). It wi ll be shown that the organic origin of this signal can be questioned. The importance of other radicals like CO33- and CO3- for EPR applicati ons will also be discussed.