-ray spectroscopy of low-lying yrast and non-yrast states in neutron-rich Kr

Gerst, R.-B.*; Blazhev, A.*; Moschner, K.*; Doornenbal, P.*; Obertelli, A.*; Orlandi, R.  ; 62 of others*

The neutron rich krypton isotopes Kr (=36, =58,59,60 respectively) were investigated at the Radioactive Isotope Beam Facility Facility (RIBF) at RIKEN. The nuclei of interest were produced in nuclear reactions induced by radioactive Kr and Rb beams, prduced via in-flight fission of U, impinging onto the liquid hydrogen target MINOS. The main reactions occurring were (p,pn), (p,p') and (p,2p). The isotopes of interest were separated in the fragment separator BigRIPS, and their rays detected using the DALI2 -ray spectrometer. The Kr provide insights onto the sudden onset of deformation occurring in Zr and Mo isotopes at =60, which is also associated with shape coexistence. In this experiment the level scheme of these isotopes could be extended, and new yrast and non-yrast states were identified. The results were compared with predictions of the "beyond-mean-field" model and the IBM model, and indications of prolate-oblate shape coexistence at =60 in the Kr isotopes was found.