Precise Measurement of Gamma-ray Emission Probabilities of 100Ru.

Abstract

To precisely determine emission probabilities of γ rays of 100Ru, β-γ coincidence measurements have been performed. A thin plastic scintillator was used to detect f rays emitted from the ground state of 100Tc produced by thermal neutron capture reaction of99 Tc, while γ rays de-exciting the excited states of 100Ru populated via the β decays were detected using a high-purity germanium detector. In the data analysis, ratios of counting rates of f rays in coincidence with one of the 100Ru γ rays to that of f-ray singles were deduced at several finite β-ray detection threshold energies. The ratios at the zero threshold energy were then deduced by extrapolating the ones at finite threshold energies to take the effect of cascading γ rays into account. From the ratios at the zero threshold energy, the emission probabilities of 539 and 591 keV γ rays of 100Ru, which are emitted following the β decay of 100Tc, were obtained to be 6.6±0.5% and 5.5±0.3%, respectively. By following the decay of the two γ rays, half-life of the 100Tc nuclide was determined to be 15.27±0.05s.