Xenon and Krypton from the Spontaneous Fission of Californium-252

The isotopic composition of xenon and krypton was measured in aluminum foils which had been exposed to ∼${10}^{10}$ fissions of ${\mathrm{Cf}}^{252}$. Relative to ${\mathrm{Xe}}^{136}$, observed yields are ${\mathrm{Kr}}^{83}$: ${\mathrm{Kr}}^{84}$: ${\mathrm{Kr}}^{85}$: ${\mathrm{Kr}}^{86}$: ${\mathrm{Xe}}^{131}$: ${\mathrm{Xe}}^{132}$: ${\mathrm{Xe}}^{134}$: ${\mathrm{Xe}}^{136}$ = 0.010:0.017:0.0049:0.032:0.35:0.52:0.90:1.000. These results show a higher relative yield at mass 134 and less fine structure in the 83-86 mass region than reported from energy-versus-time-of-flight studies on single fission fragments. Our results do not confirm the sharp minimum in the fine structure at mass 136, as suggested from radiochemical studies in the mirror mass region.