Development of an electron spin resonance spectroscopy code for measuring carbonate radicals in tooth enamel and verification of its practicality using irradiated Japanese macaque teeth

We developed a new computer program for the application of electron spin resonance (ESR) to dosimetry of wild animals related to the Fukushima Daiichi Nuclear Power Plant accident.

The ESR spectra of carbonate radicals and other inorganic radicals are calculated by the complete elliptic integral. A simulated annealing method is implemented for the parameter optimization. A cost function is designed to include the second derivative form of the microwave absorption spectrum to improve the fitting accuracy. As a testing ground for the developed code, we prepared tooth enamel samples from a Japanese macaque captured in a control area.

The developed code well reproduced the measured ESR spectrum. With a test spectrum, we demonstrated that the cost function that includes the second derivative form of the microwave absorption spectrum is helpful for the precise analysis of the low-dose enamel samples. The smoothness of the ESR spectrum plays an important role in utilizing this feature.

The developed computer code can be used to analyze the ESR spectrum of tooth enamels of Japanese macaques. A precise analysis is essential to lower the detection limit and expand the applicability of ESR dosimetry. The code is independent of the computer operating system and is available publicly.