Determination of the half-life of ^184gRe and the isomeric ratio of ^{184m, g}Re induced by D-T neutrons*

Abstract

The isomeric ratio of 184m, gRe and the half-life of 184gRe were measured in the 185Re (n, 2n) 184Re reaction at 14.8 MeV, as well as the uncertainty was discussed in detail. The measurements were performed by the activation method implemented for the rhenium sample using the K-400 neutron generator at the Chinese Academy of Engineering Physics (CAEP). Isomeric state and ground state nuclei of 184Re were identified by their γ-ray spectra. In order to eliminate the effect of the γ-ray emitted from the isomer on the counting of the ground state characteristic peak, the isomeric ratio of 184m, gRe was calculated to be 0.29 ± 0.11 according to the neutron activation cross-section formula. This result is consistent with previous data within the uncertainty, whereby it can be used to determine parameters that characterize the dependence of the level density on the excitation energy and angular momentum. Through exponential function fitting and a detailed discussion of the uncertainty evaluation, the new recommended half-life of 184gRe was determined as 35.43 ± 0.16 d, which was consistent with the currently recommended value, however, the uncertainty assessment of the latter was barely documented. In addition, this work indicates that the half-life of the ground state can be obtained by eliminating the contamination of the γ-rays emitted from the isomer, which provides the possibility to determine the half-lives of nuclides containing isomers.