Determination of the gamma and X-ray emission intensities of terbium-161.

In this study, the gamma and X-ray emission intensities of 161Tb were determined using a high-purity germanium spectrometer. The samples used were previously standardised by coincidence counting and Triple to Double Coincidence Ratio (TDCR) methods. A total of 28 gamma-rays and 4 X-rays were measured and compared with previous measurements performed more than 30 years ago. Most of the lines are in agreement, while large discrepancies are observed for 5 lines. The uncertainties have been dramatically decreased with respect to previous measurements giving a better knowledge of the 161 Tb day.