Spin-spin dependence of the total cross section ofCo59for neutrons up to 31 MeV

Abstract

The spin-spin dependence of the total cross section of ${}_{}{}^{59}{}_{}{}^{}\mathrm{Co}$ for neutrons was measured at seven energies. A polarized neutron beam with energies of 8.2, 11.1, 12.8, and 14.1 MeV from the ${}_{}{}^2{}_{}{}^{}\mathrm{H}(d,\overrightarrow{n}){}_{}{}^3{}_{}{}^{}\mathrm{He}$ reaction and of 23.0, 27.5, and 30.6 MeV from the ${}_{}{}^3{}_{}{}^{}\mathrm{H}(d,\overrightarrow{n}){}_{}{}^4{}_{}{}^{}\mathrm{He}$ reaction was transmitted through a cobalt sample. The cobalt target was cooled with a ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-${}_{}{}^4{}_{}{}^{}\mathrm{He}$ dilution refrigerator and polarized in a magnetic field. The transmission rates of the neutrons were compared for parallel and antiparallel spin orientations. The values obtained for the spin-spin cross section are much smaller than those found below 3 MeV. Deduced strengths of spin-spin terms in the optical model are in the range of 1 MeV. This is of the same order of magnitude as estimated from microscopic calculations.