Study of an asymmetric ESR signal in x-irradiated human tooth enamel

An asymmetric ESR signal and an outer doublet signal centered at g = 2.00 produced in human tooth enamel by X-irradiation have been studied over a temperature range from liquid helium temperature to 380 degrees K. The line shape of the asymmetric signal for an enamel crystallite is Lorentzian at room temperature. The temperature dependence of the integrated intensity of the asymmetric signal suggests that the signal follows a singlet-triplet model with the exchange interaction of 0.022 eV. Below about 60 degrees K the asymmetric signal becomes broad as the temperature is decreased. The ENDOR line of the asymmetric signal shows that there exists interaction between the centers and protons. The temperature dependence of the integrated intensity of the double signal is analogous to that of the asymmetric signal.