Mr Philipp Rudolf John (University and INFN Padova)
The nuclei with A~190 between Hf and Pt exhibit a great variety of nuclear phenomena, including K-isomerism, triaxiality and shape transition across the isotopic chain. This region has been in fact a crucial testing ground for the nuclear models aspiring at the description of such complex nuclear phenomena. Of particular interest is the transition from axially symmetric deformed, prolate (gamma = 0 deg.) to oblate (gamma = 60 deg.) shapes in the neutron-rich Os isotopic chain. While a study by Wheldon et al.  of the neutron-rich 194Os nucleus populated via deep-inelastic reactions suggests a prolate shape for its yrast states, Podolyak et al.  proposed an oblate shape for the ground state of 198Os by comparing the excitation energies of the first and second 2+ states. The ground state of $196Os, the even-even isotope lying between the two previously mention ones, is predicted to be prolate, oblate or gamma-soft by different state-of-the-art nuclear models. This region of the Segrè chart is very difficult to study experimentally, only fragmentation and multi-nucleon-transfer reactions can be used to populate neutron-rich nuclei in this region, hence the knowledge for this nucleus is limited to two excited states without any known gamma transition . To further elucidate this shape transition, the key nucleus 196Os was investigated in-beam using the AGATA demonstrator and the large acceptance heavy ion spectrometer PRISMA at LNL, Italy. A two nucleon transfer from a 198Pt target to a stable 82Se beam was utilised to populate medium-high spin states of 196Os. The ongoing data analysis for AGATA and PRISMA spectrometer will be discussed together with the latest results for 196Os.  C. Wheldon et al., Phys. Rev. C63, (2000) 011304(R).  Zs. Podolyak et al., Phys. Rev. C79, (2009) 031305.  P.D. Bond et al., Phys. Lett. B130, (1983) 167.
Daniele Mengoni (University and INFN Padova) Jose' Javier Valiente Dobon (INFN Legnaro) Mr Philipp Rudolf John (University and INFN Padova) Prof. Santo Lunardi (University and INFN Padova) Dr Victor Modamio Hoybjor (INFN Legnaro)