Genetic Relationships and Fission Yields of Members of the Mass-115 Decay Chain

The 21-minute ${\mathrm{Ag}}^{115}$ has been found to decay to both ${\mathrm{Cd}}^{115}$ isomers, 9 percent going to the 43-day state and 91 percent to the 53-hour state. No evidence was found for the decay of either cadmium isomer to the other. The 53-hour cadmium isomer decays to the 4.5-hour ${\mathrm{In}}^{115m}$, but <0.02 percent of the 43-day cadmium decays to ${\mathrm{In}}^{115m}$. The ${\mathrm{U}}^{235}$ thermal neutron fission yields of the 21-minute silver, 53-hour cadmium, and 43-day cadmium were determined to be 0.0078 percent, 0.0098 percent, and 0.00071 percent, respectively. All of the 43-day cadmium isomer formed in fission grows from the 21-minute silver, but 28 percent of the 53-hour isomer is formed by some other path. The fission yield of each of the cadmium isomers increases one hundred-fold when the energy of the neutrons is increased to 14 Mev. Evidence is presented for the formation of 3.5-year ${\mathrm{Cd}}^{113m}$ in approximately 5×${10}^{-5\mathrm{}}$ percent yield from the thermal-neutron fission of ${\mathrm{U}}^{235}$.