A new phenomenon—shifted identical bands and new region of stable octupole deformation

From γ-γ-γ coincidence measurements in the spontaneous fission of252Cf, level energies were established for spins 14+ to 20+ in many neutron-rich nuclei. New isotopes160Sm and162Gd were identified. The yrast bands of152,154,156Nd,156,158,160Sm, and160,162Gd exhibit remarkably near-identical transition energies and moments of inertia which are shifted by the same constant amounts for every spin state from 2+ to 12+ or 14+ for nuclei differing by 2n, 4n, 2p, 4p, α, α+2p, and α+2n. These shifted identical bands (SIB) are a new phenomenon. Analysis of all known even-even proton- to neutron-rich nuclei from Ba (Z = 56) to Os (Z = 76) reveal no SIB for proton-rich nuclei and only a few additional cases of SIB for the most neutron-rich pairs aroundN = 98–102 separated by 2n and 2p. The levels in8107Mo were extended and levels in109Mo identified for the first time.