Experimental evidences for low-lying octupole isovector states

Abstract

An evaluation of data obtained with the (n,n'γ) technique revealed in near spherical nuclei strong M1 components in transitions connecting higher-lying 3−i states with the 3−1 state. The ⟨3−1|M1|3−i⟩ matrix elements of these transitions are in the order of 1 μN. In the quadrupole sector strong ⟨2+1|M1|2+ms⟩ matrix elements serve as fingerprints for the identification of low-lying 2+ms isovector states, which are commonly referred to as mixed-symmetry states. The ratio of the two matrix elements scales for most candidates to unity indicating similar physics. Additional evidence for the assignment of the 3−i states as low-lying octupole isovector states is provided by particle-scattering experiments, e.g. (e, e') or (p, p'). The octupole states under investigation exhibit enhanced scattering cross sections. This observation is in accordance with the assignment of a one-phonon nature to these octupole excitations.