Nuclear structure of 49Ca above 5 MeV excitation from n+48Ca and astrophysics for 30 keV neutrons

The level structure of 49Ca has been investigated above the neutron separation energy by measurements of the total and capture cross sections for neutron energies up to 2 MeV. Transmission data were obtained for two 48CaCO3 samples enriched to 96% in 48Ca and were analyzed in the R-matrix formalism for neutron energies up to 2 MeV. An upper limit of 0.07x10-4 was placed upon the s-wave strength function (<Φn0>/D) and an optical model real potential was deduced from the low energy total cross section. Approximately 45% of the 2d5/2 single particle strength is observed in the region below 2 MeV neutron energy. Model configurations based on continuum shell model calculations which describe this strength and its distribution are presented. Combined low energy results are used to obtain the maxwellian averaged capture cross section and the result is discussed in relation to the nucleosynthesis of 49Ca and the anomalous abundances observed in an inclusion of the Allende meteorite. (orig.)