Photoneutron Cross Sections of Cobalt and Manganese

The total photoneutron yields of Mn⁵⁵ and Co⁵⁹ have been measured from threshold to approximately 30 Mev. Analysis of these data using the Leiss-Penfold matrix indicates that the cross sections for both elements show a splitting in the giant resonance region in accord with the predictions of the classical hydrodynamic model. The Mn⁵⁵ peaks occur at energies of 16.8±{}0.25 Mev and 19.75±{}0.25 Mev corresponding to cross sections of 90 mb and 77 mb, respectively. Co⁵⁹ maxima occur at 16.75±{}0.25 Mev and 18.75±{}0.25 Mev with cross sections of 109 mb and 92 mb. The cross sections σ(γ, n)+σ(γ, 2n)+σ(γ, np)+⋯ integrated to 25 Mev are 627 Mev-mb for Mn⁵⁵ and 709 Mev-mb for Co⁵⁹. Breit-Wigner resonance lines were fitted to both cross sections and the intrinsic quadrupole moments determined from these fits are +0.78±{}0.10 barn for manganese and +0.76±{}0.11 barn for cobalt.