Cumulative yields of the heavy fragments in U 235 thermal neutron fission

Isotopic abundances of the elements barium, cerium, neodymium, samarium and europium formed in the thermal neutron fission of U ²³⁵ have been studied with a mass spectrometer. Suitable analyses of very young and old fission products have made possible the normalization of the isotopic abundances of each of these elements through isobaric nucleides. In this manner the relative cumulative fission yield of every fission chain from mass 137 to 154 has been obtained. These yields, together with previously reported relative yields of masses 131 to 137, when normalized to total 100%, give the absolute cumulative yield of all the significant heavy fragment chains.