Collective vibrational states in even dysprosium nuclei

Abstract

The energy levels of the even dysprosium nuclei have been investigated by inelastic scattering of 12 MeV deutrons. A magnetic spectrograph was used to record the deutron spectra with an over-all energy resolution of ≈ 8 KeV. Below an excitation energy of approximately 2.5 MeV, collective octupole states, collective γ-vibrations and in some cases β-vibrations have been identified. The identifications were based on semi-empirical rules governing intensities and angular distributions of the inelastic groups. For each nucleus, most of the octupole strenght was found in a single state at approximately 1300 keV excitation. There is some evidence for this state to have K^π = 2⁻.