ISBN 9783843952897

978-3-8439-5289-7, Reihe Physik

Michael Weinert
Investigation of Microscopic Structures in the Low-Energy Electric Dipole Response of 120Sn using Consistent Experimental and Theoretical Observables and Digital Signal Processing for Nuclear Physics Experiments

148 Seiten, Dissertation Universität Köln (2022), Softcover, A5

Zusammenfassung / Abstract

This thesis consists of two parts which deal with the low-energy electric dipole response (LEDR) of atomic nuclei and the development and commissioning of a digital data acquisition system for nuclear-structure experiments, respectively. Part I tries to uncover the generating nuclear-structure features at play in the LEDR of 120Sn below the neutron-separation threshold via two complementary experiments and their theoretical comprehension. The conducted 120Sn(a,a'g) and 119Sn(d,pg) experiments are presented and nuclear-structure calculations performed within the Quasiparticle-Phonon-Model (QPM) are introduced, together with two corresponding reaction-theory approaches. Results from the (a,a'g) experiment indicate the presence of isoscalar excitations with a surface-mode character in the LEDR of 120Sn, resembling a neutron-skin oscillation. The 119Sn(d,pg) transfer experiment constitutes a novel tool to study the microscopic character of individual LEDR states. The remarkable agreement between theoretically obtained (d,pg) cross sections and the experimental data allows to benchmark the predictive power of the QPM and therein employed Energy-Density-Functional calculations. It was enforced that theory and experiment are consistently compared via identical observables and striking agreement is found for several experimentally accessible values on a quantitative level. The microscopic information, obtained for the first time in this thesis, complements the knowledge on the relevant nuclear-structure phenomena present in the LEDR of 120Sn. Part II covers the design and comissioning of a state-of-the-art digital data acquisition system. The flexible system exhibits significantly reduced dead time and reaches excellent energy resolution for gamma-ray spectroscopy.