Neutron resonance parameters and thermal-neutron capture byCa43

Neutron transmission measurements have been carried out on a small sample (205.9 mg) of ${\mathrm{CaCO}}_3$ with a ${}_{}{}^{43}{}_{}{}^{}\mathrm{Ca}$ enrichment of 49.1%. The parameters (spins and neutron widths) of eight resonances below the neutron energy of 20 keV have been determined. This information was combined with a previously measured thermal-neutron coherent scattering length to deduce the separate scattering lengths for the two spin states present in s-wave scattering. These values were used to calculate the direct (potential + valence) capture cross sections of the primary electric-dipole gamma transitions in ${}_{}{}^{44}{}_{}{}^{}\mathrm{Ca}$ using optical-model potentials with physically realistic parameters. For those states below 6.2 MeV for which the l=1 (d,p) spectroscopic factors are known, the experimental cross sections are consistent with our current understanding of the direct and compound-nuclear capture processes. The processes leading to states above 6.2 MeV require further experimental and theoretical studies.