Köln 2025 – wissenschaftliches Programm

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HK: Fachverband Physik der Hadronen und Kerne

HK 26: Structure and Dynamics of Nuclei VII

HK 26.4: Vortrag

Mittwoch, 12. März 2025, 15:00–15:15, HS 2 Physik

First measurement of the lifetime of the 2₁⁺ state of ²⁰⁰Pt — •C.M. Nickel¹, V. Werner¹, P.R. John¹, U. Ahmed¹, C. Costache², K.E. Ide¹, N.M. Mărginean², H. Mayr¹, C. Mihai², R.E. Mihai^2,3, N. Pietralla¹, T. Stetz¹, A. Weber¹, and R. Zidarova¹ — ¹IKP, TU Darmstadt — ²IFIN-HH, Bucharest-Măgurele — ³IEAP, CTU Prague

The W, Os, Pt and Hg isotopes exhibit shape transitions between oblate, prolate, γ-soft and spherical nuclei [1]. The neutron-rich Pt isotopes transition from γ-softness towards sphericity, as indicated by the energy ratio R_4/2, when approaching the neutron-shell closure at N = 126. In the vicinity of shell closures, quadrupole collectivity is expected to decrease and, hence, the B(E2; 2₁⁺ → 0₁⁺) transition strength which is inversely proportional to the lifetime of the 2₁⁺ state. ²⁰⁰Pt is the lightest neutron-rich Pt isotope without a known B(E2; 2₁⁺ → 0₁⁺) value and could sit at the transitional point between a γ-soft and a spherical shape. Therefore, the ¹⁹⁸Pt(¹⁸O,¹⁶O)²⁰⁰Pt* two-neutron transfer reaction was studied in a recoil-distance Doppler-shift experiment at the IFIN-HH in Bucharest-Măgurele using the ROSPHERE array equipped with 25 HPGe detectors and the SORCERER particle detector. Correcting for contaminants as well as taking de-orientation into account, allowed the application of the differential decay curve method to determine the lifetime of 2₁⁺ state of ²⁰⁰Pt for the first time. The analysis and resulting B(E2; 2₁⁺ → 0₁⁺) value will be presented.

[1] Z. Podolyák et al., Phys. Rev. C 79 031305 (2009).

*Supported by the BMBF under Grant No. 05P21RDCI2.

Keywords: 200Pt; RDDS; DDCM; Lifetime measurement; ROSPHERE + SORCERER