Neutron capture cross sections of Hf-178 leading to Hf-179(m2)

摘要

Cross sections for radiative neutron capture have been measured for the formation of 25-d Hf-179(m)2 (J(pi) = 25/2(+)) using targets of enriched Hf-178. Based on irradiations using pure epithermal neutrons as well as mixed thermal + epithermal neutrons, the thermal cross section has been determined to be sigma = 6(5) mu b and the resonance integral I = 1.63(5)mb. To enhance the determination of the cross sections, the energies and intensities of the gamma rays from the decay of Hf-179(m)2 have been re-determined with improved precision. The half-life of Hf-179(m2) has been measured to be 24.91(27) d, in agreement with the previously accepted value. The analysis of the Hf-179(m)2 decay required more precise spectrometry on competing gamma rays from the decay of Hf-181, whose results are presented (along with that of the decay of Hf-175) from irradiation of a source of natural Hf. The measured cross sections are compared with those of other high-spin neutron captures.