6533b7d7fe1ef96bd1268d81

RESEARCH PRODUCT

Nuclear-structure input to r-process calculations

subject

description

Abstract By comparing results from r-process parameter studies within the classical waiting-point approximation with the observed solar-system r-abundance distribution N r ,⊙ , in-formation on nuclear-structure phenomena on neutron-rich isotopes far off the stability line can be obtained. Such information is — to a large extent — experimentally not accessible. Investigations in the early 1990's, making use of QRPA β-decay properties and nuclear masses from the macroscopic-microscopic FRDM and ETFSI-1 models, showed r-abundance deficiencies around A ⋍115 and 180 , indicating overly strong N=82 and 126 shell strengths far from stability. Recent experiments in the A ⋍110–130 region as well as more microscopic mass models, such as the spherical HFB/SkP ansatz and the deformed ETFSI-Q formalism, seem to confirm our earlier predictions, in particular shell-quenching and neutron-skin effects. These new nuclear-structure phenomena have important astrophysical implications for r-process calculations. Not only do they result in a considerable improvement of the global N r ,⊙ fits, but also they put tighter constraints on the neutron densities required and on the duration of the r-process. Moreover, abundance calculations of the classical r-process cosmochronometers are now based on an internally consistent nuclear-physics input, which allows meaningful comparisons with the latest astronomical observations of ultra-metal-poor halo stars.