Münster 2017 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 56: Hauptvorträge IV

HK 56.1: Invited Talk

Friday, March 31, 2017, 11:00–11:40, F 1

The origin of low-lying collective E1 and E2 strength in atomic nuclei — •Mark Spieker — Institute for Nuclear Physics, University of Cologne

In the atomic nucleus, global isospin symmetry between the constituent protons and neutrons has often been considered as a feature of the strong interaction 1 . However, it is a well-known fact that rather local than global isospin symmetry is realized, see, e.g., 2 . Low-lying collective E1 and E2 strengths provide a powerful tool to study the mechanisms by which isospin symmetry is fully or partly broken. In this talk two generating mechanisms of electric dipole and quadrupole collectivity below the particle-emission thresholds will be discussed. First, the α-cluster dipole mode, i.e. the dipole-type oscillation of an α-particle against the remaining bulk will be introduced as a possible generator of low-lying E1 strength in medium-mass and heavy nuclei 3 . Secondly, the comprehensive experimental study of E2 strength in the Sn isotopes will be presented to highlight the quadrupole-type oscillation of the neutron skin against the isopin-saturated core as a possible generator of low-lying E2 strength 4 .

Supported by the DFG (ZI 510/7-1).
1  D.D. Warner, M.A. Bentley, P. Van Isacker, Nature Physics 2, 311 (2006)
2  F. Iachello, Phys. Lett. B 160, 1 (1985)
3  M. Spieker, S. Pascu, A. Zilges, F. Iachello, Phys. Rev. Lett. 114, 192504 (2015)
4  M. Spieker, N. Tsoneva et al., Phys. Lett. B 752, 102 (2016)