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HK: Fachverband Physik der Hadronen und Kerne

HK 53: Structure and Dynamics of Nuclei XI

HK 53.1: Group Report

Wednesday, March 13, 2024, 17:30–18:00, HBR 19: C 5b

The lowest-lying mixed-symmetry 2⁺ state in the N=80 isotones — •T. Stetz¹, H. Mayr¹, N. Pietralla¹, G. Rainovski², V. Werner¹, and R. Zidarova¹ — ¹Technische Universität Darmstadt, Germany — ²Sofia University St. Kliment Ohridski, Bulgaria

Quadrupole collectivity near closed shells manifests in the known 2₁⁺ proton-neutron symmetric one quadrupole-phonon excitation of the valence shell and its isovector proton-neutron mixed-symmetric 2_ms,1⁺ counterpart. Their respective character is quantified by the F-spin quantum number. A direct influence of subshell structure on the properties of the 2_ms,1⁺ state has first been observed in ¹³⁸Ce by Rainovski et al. [1]. This lack of shell stabilization leads to a distribution of the M1 strength of the 2_ms,1⁺ configuration to the 2₁⁺ state over several excited 2⁺ states of ¹³⁸Ce. In contrast, the B(M1;2_i⁺ → 2₁⁺) strength in other N=80 isotones below the g_7/2 subshell closure is isolated in a single 2⁺ state [2,3]. A recent two neutron-transfer experiment to determine the B(M1;2₂⁺ → 2₁⁺) of ¹³²Te supports these observations. Furthermore, a single pronounced one-quadrupole phonon 2_ms,1⁺ state has been found in ¹⁴⁰Nd and ¹⁴²Sm through Coulomb-excitation experiments, showing a restoration of F-spin symmetry above ¹³⁸Ce [4,5].

[1] G. Rainovski et al., Phys. Rev. Lett. 96 (2006) 122501

[2] T. Ahn et al., Phys. Lett. B 679 (2009) 1

[3] N. Pietralla et al., Phys. Rev. C 58 (1998) 796

[4] R. Kern et al., Phys. Rev. C 102 (2020) 041304(R)

[5] R. Kern et al., J. Phys.: Conf. Ser. 1555 (2020) 012027

*Supported by BMBF 05P18RDCIA and 05P21RDCI2

Keywords: mixed-symmetry states; shell stabilization