In-beam gamma-ray spectroscopy of the neutron-rich platinum isotope Pt 200 toward the N=126 shell gap

The neutron-rich nucleus\ nucleus{200}{Pt} is investigated via in-beam \ gamma-rayspectroscopy in order to study the shape evolution in the neutron-rich platinum isotopes towards the N = 126 shell closure. The two-neutron transfer reaction \ nucleus{198}{Pt}(\ nucleus{82}{Se}, \ nucleus{80}{Se})\ nucleus{200}{Pt} is used to populate excited states of \ nucleus{200}{Pt}. The Advanced Gamma RayTracking Array ( AGATA) demonstrator coupled with the PRISMA spectrometer detects \ gamma rayscoincident with the \ nucleus{80}{Se} recoils, the binary partner of \ nucleus{200}{Pt}. The binary partner method is applied to extract the \ gamma-raytransitions and build the level scheme of \ nucleus{200}{Pt}. The level at 1884\,keV reported by Yates et. al [Phys. Rev. C 37, 1889] was confirmed to be at 1882.1\,keV and assigned as the (6^+_1) state. An additional \ gamma raywas found and it presumably de-excites the (8^+_1) state. The results are compared with state-of-the-art beyond mean-field calculations, performed for the even-even \ nucleus{190-204}{Pt} isotopes, revealing that \ nucleus{200}{Pt} marks the transition from the \gamma-unstable behaviour of lighter Pt nuclei towards a more spherical one when approaching the N=126 shell closure.