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

The neutron-rich nucleus 200Pt is investigated via in-beam γ-ray spectroscopy to study the shape evolution in the neutron-rich platinum isotopes towards the N=126 shell closure. The two-neutron transfer reaction 198Pt(82Se, 80Se)200Pt is used to populate excited states of 200Pt. The Advanced Gamma Ray Tracking Array (AGATA) demonstrator coupled with the PRISMA spectrometer detects γ rays coincident with the 80Se recoils, the binary partner of 200Pt. The binary partner method is applied to extract the γ-ray transitions and build the level scheme of 200Pt. The level at 1884 keV reported by Yates et al. [S. W. Yates, E. M. Baum, E. A. Henry, L. G. Mann, N. Roy, A. Aprahamian, R. A. Meyer, and R. Estep, Phys. Rev. C 37, 1889 (1988)] was confirmed to be at 1882.1 keV and assigned as the (6+1) state. An additional γ ray was found and it presumably deexcites the (8+1) state. The results are compared with state-of-the-art beyond mean-field calculations, performed for the even-even 190−204Pt isotopes, revealing that 200Pt marks the transition from the γ-unstable behavior of lighter Pt nuclei towards a more spherical one when approaching the N=126 shell closure.