ISBN 978-3-8439-4908-8

978-3-8439-4908-8, Reihe Physik

Felix Heim
The statistical γ-decay behavior and nuclear reaction rates of heavy nuclei relevant for explosive nucleosynthesis

154 Seiten, Dissertation Universität Köln (2021), Softcover, A5

Zusammenfassung / Abstract

To understand the production processes of chemical elements that take place inside of stars detailed knowledge about the underlying nuclear physics processes is necessary. For nuclear reactions that are not accessible experimentally, reliable theoretical extrapolations are required. Among the most important ingredients related to nuclear physics for those calculations are the nuclear level density (NLD) and the γ-ray strength function (γ-SF).

The present cumulative thesis comprises six publications in peer-reviewed journals. The thesis reports on four nuclear reactions around the A = 100 mass region. The nuclear reactions investigated by means of in-beam γ-ray spectroscopy in this thesis are the 107Ag(p,γ)108Cd, 109Ag(p,γ)110Cd and 93Nb(p,γ)94Mo reactions while the 96Mo(p,n)96m,gTc reaction has been measured using the activation technique. In addition, within the scope of this thesis the experimental setup that is used for cross-section measurements relevant for nuclear astrophysics has been revised.

The radiative proton capture experiments on the stable silver isotopes 107Ag and 109Ag provided the first set of measured cross sections over a wide range of energies for the respective reactions. In addition, partial cross sections have been extracted allowing to directly investigate the γ-SF in 108Cd. The 93Nb(p,γ)94Mo reaction can affect the overall abundance of the neutron-deficient nucleus 94Mo. Primary γ rays have been used to constrain the γ-SF in 94Mo. The individual 96Mo(p,γ)96m,gTc cross sections have been measured as well a the 96mTc to 96Mo decay intensity has been remeasured.

A strategic approach has been applied to test the predictive power of theoretical models for those properties. It was found that for the NLD microscopic models provide much more reliable predictions compared to simple phenomenological models. The results for the γ-SF in 108Cd and 94Mo are in good agreement with recent microscopic calculations.