Abstract: EPR dating is based on the detection of paramagnetic center created by natural radioactivity in a sample. The thermal stability of the paramagnetic center is related to the characteristics of the structure of the sample and the environmental temperature of sample site. We use mean life τ to express the thermal stability. Because the limit of EPR dating depends on the mean life, the research of thermal stability is an important part of fundamental researches for EPR dating. We studied thermal stability of diffrent paramagnetic centres of five samples by isothermal annealing experiments, and determined their mean life at 20℃,activation energy and frequency factor respectively.

Key words: Paramagnetic center, Thermal stability, Mean life