Yields of Krypton Isotopes from the Deuteron and Alpha Bombardment of Heavy Nuclei

The relative yields of 4.4-hr ${\mathrm{Kr}}^{85m}$, 78-min ${\mathrm{Kr}}^{87}$, and 2.8-hr ${\mathrm{Kr}}^{88}$ have been measured radiochemically for the fission of ${\mathrm{Th}}^{232}$, ${\mathrm{U}}^{235}$, and ${\mathrm{U}}^{238}$ induced by 14- and 9-Mev deuterons and 25-Mev alpha particles. Yields of these nuclides were also determined for the fission of ${\mathrm{U}}^{235}$ with thermal neutrons. By correcting for charge distribution, relative chain yields were obtained for mass numbers 85, 87, and 88. The results for thermal neutron fission of ${\mathrm{U}}^{235}$ are in good agreement with mass-spectrometrically determined yields at these mass numbers. Deviations from smooth yield-mass curves are found for deuteron fission of ${\mathrm{Th}}^{232}$ and alpha-particle fission of ${\mathrm{Th}}^{232}$, ${\mathrm{U}}^{235}$, and ${\mathrm{U}}^{238}$, whereas deuteron fission of ${\mathrm{U}}^{235}$ and ${\mathrm{U}}^{238}$ show normal mass yields. The origin of these fine-structure effects is not understood, but no evidence has been found for a systematic influence of the 50-neutron shell in perturbing the fission yields in the krypton mass region.