Excitation study of high-lying states of differently shaped heavy nuclei by the method of two-step cascades

Abstract

Recently obtained primary transition intensities from two-step gamma-ray cascade investigations of 14 heavy nuclei: 137,138,139 Ba, 146 Nd, 150 Sm, 156,158 Gd, 160 Tb, 164 Dy, 168 Er, 174 Yb, 181 Hf, 196 Pt and 198 Au are analysed. Experiments based on thermal neutron capture were undertaken mainly at the Frank Laboratory of Neutron Physics. Comparing these measured intensities and statistical model predictions, some properties of compound-state depopulation were derived. For the spherical nuclei of 137,138,139 Ba, 146 Nd, 196 Pt and 198 Au very intense cascades with high-energy primary transitions were observed. Rather different is the behaviour of the cascade intensity in the strongly deformed nuclei of 156,158 Gd, 160 Tb, 164 Dy, 168 Er and in the transitional nucleus of 150 Sm - where the intensity of primary γ-rays E 1 ∼ 2–3 MeV exceeds the calculated value.