IDENTIFICATION AND DECAY OF U-242 AND NP-242

The nuclides U242 and Np242 were discovered by chemical separations from targets of Pu244 irradiated with 30-160 MeV neutrons followed by γ-ray and β-ray spectroscopy. The parent U242 decays with T12=16.8±0.5 min; 14 γ rays ranging from 55.6 keV to 585.0 keV were assigned to its decay. The Np242 daughter half-life is 2.2±0.2 min and 39 γ rays following its decay have energies between 620.6 and 2370.5 keV. Qβ- of Np242 is 2.7±0.2 MeV. A level scheme is proposed for Pu242 in which the lowest 7 levels were previously described and 12 new levels are shown. The ground state of Np242 is assigned Iπ=1+ and 6 excited levels are proposed which accommodate most of the observed γ rays from decay of U242. RADIOACTIVITY U242, Np242 from Pu244(n,2pn)U242→β-Np242; radiochemistry, Ge(Li) and plastic detectors. U242: measured T12, Eγ, Iγ; deduced Eβ-, Iβ-, logft, decay scheme, J, π, Nilsson state assignments. Np242: measured T12, Eγ, Iγ, Eβ-, Iβ-; deduced logft, decay scheme, J, π, Nilsson assignments. © 1979 The American Physical Society.