Measurement of gamma-ray emission probabilities using a combination of activation and oscillation techniques: applications to 171Er, 181Hf, 233Pa and 243Pu

Emission probabilities of γ-rays are one of the most important decay parameters and reduction of their uncertainty is required in many fields of nuclear physics. For some radionuclides, a direct measurement of these parameters is not achievable with a sufficient accuracy due to the limitations of the usual experimental techniques. In this paper, an innovating method for measuring some γ-ray emission probabilities is proposed. It is based on the combination of oscillation and activation techniques. On one hand, the oscillation measurements provide an accurate estimation of the integral absorption cross sections of the studied isotope. On the other hand, the integral capture cross sections are also determined by γ-ray spectrometry using the relevant γ-rays of the capture product. The comparison of those independent results gives a direct and accurate assessment of the γ-ray emission probabilities. The combined method is fully described, as well for instruments and conditions as for the control of the uncertainties. It is applied to the cases of 171Er, 181Hf, 233Pa and 243Pu. The study enlightens an overestimation of (19.1 ± 20.5)%, (28.6 ± 12.7)% and (20.0 ± 12.3)% of the JEFF3.1 emission probabilities of the most intense γ-ray of respectively 171Er, 181Hf and 243Pu. In the near future, this technique will be applied to 238Np and 244Am