Formation ofCd115Isomers in High-Energy Fission of Bismuth

The relative yields and recoil properties of the ${\mathrm{Cd}}^{115}$ isomers independently formed in the 450-Mev proton fission of bismuth have been measured. The 43-day ${\mathrm{Cd}}^{115m}$ isomer has a higher yield and smaller range than the 53-hr ${\mathrm{Cd}}^{115}$. ${\mathrm{Cd}}^{115m}$ is also formed in a higher deposition energy process than ${\mathrm{Cd}}^{115}$. These results are explained in terms of the high-spin states of the fission fragments resulting both from the high bombarding energy and from the fission act proper.