Neutron reactions in astrophysics

Abstract

The quest for the origin of matter in the Universe had been the subject of philosophical and theological debates over the history of mankind, but quantitative answers could be found only by the scientific achievements of the last century. A first important step on this way was the development of spectral analysis by Kirchhoff and Bunsen in the middle of the 19 th century, which provided first insight in the chemical composition of the sun and the stars. The energy source of the stars and the related processes of nucleosynthesis, however, could be revealed only with the discoveries of nuclear physics. A final breakthrough came eventually with the compilation of elemental and isotopic abundances in the solar system, which are reflecting the various nucleosynthetic processes in detail.This review is focusing on the mass region above iron, where the formation of the elements is dominated by neutron capture, mainly in the slow (s) and rapid (r) processes. Following a brief historic account and a sketch of the relevant astrophysical models, emphasis is put on the nuclear physics input, where status and perspectives of experimental approaches are presented in some detail, complemented by the indispensable role of theory.

Carbon-enhanced metal-poor stars: a window on AGB nucleosynthesis and binary evolution

“…For a thorough discussion of these scenarios we refer to Jonsell et al (2006) and Lugaro et al (2009). Lugaro et al (2009) suggest a third speculative scenario in which r-and s-elements are both formed in low-mass extremely metalpoor AGB stars ([Fe/H] < −3), that may be able to produce very high densities of free neutrons when protons are ingested in the region of the He-flash (Campbell 2007;Campbell & Lattanzio 2008;Herwig et al 2011;Reifarth et al 2014). …”

p-process nucleosynthesis via proton-capture reactions in thermonuclear supernovae explosions

“…In a first step, the target material has to be produced. An amount of 10 16 nuclei should be sufficient to perform the experiment taking into account the proton-beam intensity and detection system under construction at FRANZ, Frankfurt a. M., Germany [29]. One way to produce 91 Nb is the bombardment of 92 Mo with protons.…”

Neutron capture cross sections of Kr

“…There are two major processes, the rapid neutron-capture process (rprocess) and the slow neutron capture process (s-process) [4]. Only a few isotopes on the proton-rich side of the valley of stability get significant contributions from other processes.…”