Nuclear levels in 160Tb

Abstract The high energy γ-ray spectrum from thermal neutron capture in natural terbium has been studied over the energy range of 5200 to 6400 keV. Low energy γ-radiation of the same reaction has been observed from 20 to 1230 keV and conversion electrons from 6 to 160 keV. Low energy (n, γγ) coincidences have been measured. A value of 6375.1 ± 0.3 keV has been obtained for the neutron binding energy in 160 Tb. The data, when combined with a previous 159 Tb (d, p) study, allow a level scheme to be constructed. These levels are assigned to nine rotational bands built on two quasiparticle configurations. The decay of several other levels is discussed. In three cases we have observed both parallel and antiparallel coupled bands with K − = ¦Ω p −Ω n ¦ and K + = Ω p + Ω n , and found the Gallagher-Moszkowski rule to be valid. The energy splitting has been calculated using Nilsson wave functions and a δ-force. Two K = 1 bands with irregular level spacing have been observed.