RADIOISOTOPES

The purpose of the present study is to establish a new convenient detection method for γ-ray irradiation history. To measure very weak thermal emission spectra of γ-irradiated seashells, a new multichannel Fourier-transform chemiluminescence spectrometer, an interferometer of which is composed of a Savart plate, a quartz lens, and two linear polarizers, was used. When irradiated mussel shells were cleaned by water, crushed by a freezing crusher, and heated at 473 K, spatial interferogram was obtained from signals on each CCD pixel, which was converted to thermal emission spectra by Fourier transformation. The observed spectra were modeled with one Gaussian curve by least-squares fitting, showing a peak position at about 641 nm. We found that the spectral intensity depends on the dose of γ-ray irradiation and the history of 0.1 kGy irradiation is detectable. In addition, the emission spectrum of a sample washed by only water was found to be similar to that washed by 5％ NaOCl solution, meaning that the washing by the solution is not required. The method proposed in the present study is expected to develop as a new convenient method to know the γ-ray irradiation history of seashells.