Fission fragment angular momentum: Independent isomeric yield ratio of 138Cs in thermal neutron induced fission of 233U, 239Pu and 241Pu

The independent isomeric yield ratio of 138Cs in the thermal neutron induced fission of 233U, 239Pu and 241Pu has been determined by fast radiochemical separation followed by gamma-ray spectrometry. The yield ratios sigmasub(h)/(sigmasub(h)+sigmasub(l)) are 0.72+-.04, 0.67+-.06 and 0.65+-.11 for 233U(nsub(th),f), 239Pu(nsub(th),f) and 241Pu(nsub(th),f), respectively. These values correspond to the average angular momenta (Jsub(av)) of 9.3+-0.7 (h/2π), 8.2+-1.3 (h/2π) and 7.6+-1.2 (h/2π) for the respective nuclides undergoing fission. The present results in combination with data from the literature corroborate a marked odd-even effect on fragment angular momenta with the odd-Z fragments having relatively larger angular momenta than the neighbouring even-Z ones. (orig.)