Cross section measurements and thermonuclear reaction rates for ^(48)Ca(p, γ)^(49)Sc and ^(48)Ca(p, n)^(48)Sc

Abstract

Absolute cross sections have been measured for the reaction ^(48)Ca(p, γ)^(49)Sc for 0.579 MeV ≦ Ep, lab ≦ 2.670 MeV and for the reaction ^(48)Ca(p, n)^(48)Sc for 0.956 MeV ≦ E_(p,lab) ≦ 2.670 MeV. Substantial competition effects in the cross section for ^(48)Ca(p, γ)^(49)Sc were observed at the thresholds for neutron emission to the 623 keV (3^+), 1143 keV (2^+) and 1402 keV (2^−) excited states of ^(48)Sc. Thermonuclear reaction rates were calculated from the measured cross sections for 0.1 ≦ T_9 ≦ 10.0. The new rates differ considerably from those used in earlier calculations of the production of the rare, neutron-rich intermediate mass nuclides during explosive carbon burning. In particular, the new rates may change the predicted abundances for ^(48)Ca, ^(49,50)Ti and ^(50)V substantially. The good agreement between current global Hauser-Feshbach models and the experimental data indicates that Hauser-Feshbach calculations can provide sufficiently reliable rates for astrophysical calculations in cases where experimental data are non-existent.

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