Change of the dipole strength distributions between the neighbouring γ-soft nuclei 194Pt and 196Pt

Abstract

A nuclear resonance fluorescence experiment with two highly efficient EUROBALL Cluster detectors has been performed on the γ-soft nucleus 194Pt. Dipole excitations were observed between 2 and 4 MeV excitation energy. They are tentatively interpreted as the main fragments of the scissors mode based on the measured excitation strengths and a comparison to microscopic calculations in the framework of the quasiparticle random phase approximation (QRPA). The data indicate large differences to the neighbouring isotope 196Pt: a doubling of the observed dipole strength and a shift of the energy centroid by about 600 keV. None of the currently available models is able to reproduce these features consistently in both nuclei.