High precision measurements for the rp-process

Abstract

The explosive nuclear burning of hydrogen at high temperatures and densities on the surface of accreting neutron stars, known as the rp-process, gives rise to a number of observable phenomena related to X-ray bursts. Recent astronomical observations provide unprecedented information, e.g. on atomic abundances in ejecta and time structure in X-ray bursts. To interpret these data requires an understanding of the nuclear processes during the explosive events and, therefore, information on the structure of unstable, proton-rich nuclei. Network model calculations show that the dominant burning processes, after breakout from the hot CNO cycles at sufficiently high temperatures, proceed via proton- and α-induced reactions. Since the reaction rates are very sensitive to the nuclear structure, shell- and statistical-model calculations are often insufficient in predicting exact reaction paths. Therefore, we have been conducting experiments using high-resolution spectrometers to search for resonances that play a role in the rp-process and determine the nuclear-structure, most importantly excitation energies, accurately above the particle thresholds. The techniques and examples of experimental results will be presented and discussed. The status and outlook of direct measurements of stellar reactions rates in inverse kinematics using planned recoil separators will be outlined. © Published under licence by IOP Publishing Ltd.