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

Abstract

A nuclear resonance fluorescence experiment with two highly efficient EUROBALL Cluster detectors has been performed on the gamma-soft nucleus Pt-194. 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 Pt-196: 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. (C) 2002 Elsevier Science B.V All rights reserved.