Spin distribution factors for formation of metastable states of 90Y and 91Y through (n,p) reactions over neutron energies 5–15 MeV

Abstract

The variations in the isomer ratio with the spin distribution factor were studied to obtain the cross-sections for formation of metastable states of 90Y and 91Y nuclei formed respectively through 90Zr(n,p) 91Y m and 91Zr(n,p) 91Y m reactions over the neutron energy range 5 to 15 MeV. The theoretical values of the cross-sections could be obtained very close to the respective literature experimental values by varying the spin distribution factor from 1.5 to 2.75. The limiting value of the cross-section was derived from the maximum value of the isomer ratio at that neutron energy, and for this the spin distribution factor was found to vary from 2 to 3.5 over the neutron energies 5 to 15 MeV. Using enriched zirconium targets, cross-sections for formation of 90Y m and 91Y m nuclei at 14.8 MeV neutron energy were also measured in the laboratory; the values obtained are 17 ± 2 mb and 22 ± 2 mb respectively for 90Y m and 91Y m. Both these values are close to the corresponding limiting cross-sections at 14 MeV neutron energy.