Radioactive decay studies at TRISTAN. Progress report, December 1, 1981-December 31, 1982

It was found possible to interpret the levels of the odd-odd N = 83 nuclides by parabolic fits to plots of multiplet splitting versus I(I + 1). Parameters are found that account for the splitting, displacement and inversion of these multiplets. It is concluded that the interaction between the odd proton and odd neutron in the N + 83 nuclides is largely a quadrupole interaction. Moreover, the effect of odd I-even I staggering that comes from the delta interaction is not significant. Using the parabolic parameters for 140La, it is possible to project the low-lying multiplets in 142La and compare them with the new level scheme that has been completed for 142La. The density of observed levels is in accord with the projection and the new 0.87 μs isomer lies at the vertex of one of the paraboli. The first PAC measurements at TRISTAN have been concluded and g factors determined for the first 2+ states in 144Ba and 146Ba. New level schemes for odd-odd 146La, 148La, and 148Pr reveal sharp differences in the behavior of the 1+ levels in Pr versus La as neutron pairs are added beyond the closed shell at N + 82. These changes are most important at N + 88. Two new isomers have been identified, a 5 ns level at 48 or 55 keV in 141La and an 870 ns level at 145 keV in 142La. Additional evidence for isomerism in 148Pr has been obtained by careful measurements of the half lives of several intense ν rays and by measuring the intensity of 148Pr ν rays as power is varied on the ion source