Bonn 2020 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 7: Structure and Dynamics of Nuclei II

HK 7.3: Talk

Monday, March 30, 2020, 17:15–17:30, J-HS H

Isovector-E2 strength of the scissors mode of ¹⁵²Sm — •K.E. Ide¹, T. Beck¹, M. Berger¹, S. Finch², U. Friman-Gayer¹, J. Kleemann¹, FNU Krishichayan², B. Löher¹, O. Papst¹, N. Pietralla¹, D. Savran³, W. Tornow², M. Weinert⁴, V. Werner¹, and J. Wiederhold¹ — ¹IKP, TU Darmstadt — ²TUNL, Duke University, Durham NC, USA — ³GSI, Darmstadt — ⁴IKP, Universität zu Köln

The nucleus ¹⁵²Sm is well known to be located at the N=90 quantum shape-phase transition (QSPT) boundary, mainly set by the residual forces between valence protons and neutrons. Since the scissors mode (SM) is a collective, isovector excitation, its decay characteristics are highly dependent on these forces and sensitive to the QSPT. The SM is known for its M1-excitation strength, however, data on isovector E2 properties are sparse [1]. The SM of ¹⁵²Sm was investigated in a nuclear resonance fluorescence experiment performed at the High-Intensity γ-Ray Source with a quasi-monoenergetic, polarized photon beam with an energy of 2.99(5) MeV. Emitted photons were detected by four high-purity germanium detectors positioned at angles sensitive to the multipolarities of the decay radiation of 1^π states. The isovector E2 transition of the SM of ¹⁵²Sm to its first 2⁺ state has been deduced from the E2/M1 multipole mixing ratio of the 1_sc⁺ → 2₁⁺ transition. Experimental results are compared to predictions of the interacting boson model 2, yielding proton and neutron effective boson charges.

*Supported by the DFG under grant No. SFB 1245

[1] T.Beck et al., Phys. Rev. Lett. 118 (2017) 212502