ISBN 9783843929714

978-3-8439-2971-4, Reihe Physik

Mark-Christoph Spieker
The origin of low-lying collective E1 and E2 strength in atomic nuclei

135 Seiten, Dissertation Universität Köln (2016), Softcover, A5

Zusammenfassung / Abstract

In the atomic nucleus, global isospin symmetry between the constituent protons and neutrons has often been considered as a feature of the strong interaction. However, it is a well-known fact that rather local than global isospin symmetry is realized. 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 thesis, two generating mechanisms of electric dipole and quadrupole collectivity below the particle-emission thresholds are discussed. First, the alpha-cluster dipole mode, i.e. the dipole-type oscillation of an alpha-particle against the remaining bulk is introduced as a possible generator of low-lying E1 strength in medium-mass and heavy nuclei. Secondly, the comprehensive experimental study of E2 strength in the Sn isotopes is 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.