Determination of the neutron-capture rate of ^{17}C for rprocess nucleosynthesis With the R 3 B-LAND setup at GSI we have measured exclusive relative-energy spectra of the Coulomb dissociation of 18 C at a projectile energy around 425 AMeV on a lead target, which are needed to determine the radiative neutron-capture cross sections of 17 C into the ground state of 18 C. Those data have been used to constrain theoretical calculations for transitions populating excited states in 18 C. This allowed to derive the astrophysical cross section σ * nγ accounting for the thermal population of 17 C target states in astrophysical scenarios. The experimentally verified capture rate is significantly lower than those of previously obtained Hauser-Feshbach estimations at temperatures 2 T9 ≤ 1 GK. Network simulations with updated neutron-capture rates and hydrodynamics according to the neutrino-driven wind model as well as the neutron-star merger scenario reveal no pronounced influence of neutron capture of 17 C on the production of second-and third-peak elements in contrast to earlier sensitivity studies.
Neutron-rich light nuclei and their reactions play an important role for the creation of chemical elements. Here, data from a Coulomb dissociation experiment on 20,21 N are reported. Relativistic 20,21 N ions impinged on a lead target and the Coulomb dissociation cross section was determined in a kinematically complete experiment. Using the detailed balance theorem, the 19 N(n, γ) 20 N and 20 N(n, γ) 21 N excitation functions and thermonuclear reaction rates have been determined. The 19 N(n, γ) 20 N rate is up to a factor of 5 higher at T < 1 GK with respect to previous theoretical calculations, leading to a 10 % decrease in the predicted fluorine abundance.
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