Isomeric Ratios in Reactions Induced by Gamma Rays and Fast Neutrons in the Isotopes of Re, Ir, and Au

摘要

Isomeric ratios were measured in the (γ, n) and (n, 2n) reactions leading to the formation of ~(184)Re, ~(190)Ir, and ~(196)Au odd–odd nuclides. The measurements were performed by the activation method implemented for Re, Ir, and Au samples of natural isotopic composition that were irradiated with 14.7-MeV neutrons and bremsstrahlung photons of endpoint energy 22 MeV. Isomeric- and ground-state nuclei formed in these reactions were identified by their x- or γ-ray spectra and by their half-lives. The isomeric ratios were calculated on the basis of the statistical model, and the results were compared with experimental data, whereby it was possible to determine parameters that characterize the dependence of the level density on the excitation energy and angular momentum. The effect of the nuclear structure on these parameters is discussed.