Experimental evidences for low-lying octupole isovector states

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 ##IMG## [http://ej.iop.org/icons/Entities/langle.gif] langle 3 − 1 | M 1|3 − i ##IMG## [http://ej.iop.org/icons/Entities/rangle.gif] rangle matrix elements of these transitions are in the order of 1 μN. In the quadrupole sector strong ##IMG## [http://ej.iop.org/icons/Entities/langle.gif] langle 2 + 1 | M 1|2 + ms ##IMG## [http://ej.iop.org/icons/Entities/rangle.gif] rangle 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.