In-beam γ -ray spectroscopy of the neutron-rich platinum isotope 200Pt 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 (6₁⁺) state. An additional γ ray was found and it presumably deexcites the (8₁⁺) state. The results are compared with state-of-the-art beyond mean-field calculations, performed for the even-even ^{190 -204}Pt 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.