Nuclear charge distribution in fission: fractional cumulative yields of isotopes of krypton and xenon in 249 Cf(n th ,f) and 250 Cf(sp.f)

The fractional cumulative yields (%) of the following rare gas isotopes were determined radiochemically in the thermal neutron induced fission of 249 Cf and in the spontaneous fission of 250 Cf and the following results were obtained for the two processes, respectively: 89 Kr: 77.6 ± 1.5, —; [Formula: see text], [Formula: see text]; [Formula: see text]; 139 Xe: 32.0 ± 3.5, 23.6 ± 6.0; 140 Xe: 12.5 ± 2.0, 14.7 ± 7.0; 141 Xe: 4.0 ± 0.3, [Formula: see text]; 142 Xe: 0.9 ± 0.1, ≤ 3.61, and 143 Xe: 0.22 ± 0.08, —. The results are discussed with respect to the systematies of nuclear charge distribution in fission.