The odd-parity level at 687.59 keV in236U

The spin-parity of the 687.59 keV level in236U populated in the decay of236Np is determined to be 2− in disagreement with recent 1− assignments from reaction data, but in accordance with previous radioactive236Np decay studies. The 687 keV ground state transition is shown to have a pureM2 character. The 642 keV 2−→2+ transition hasE1:M2:E3 mixing ratios of 64∶30∶6. The half-life of the 2− state is 3.78 ± 0.09 ns. The hindrance factor of the E1-part fits an E1 transition withΔK=2, theM2-part has the same transition rate as the M2 transitions in the neighbouring237Np nucleus and the E3-part is enhanced by two orders of magnitude relative to the Weisskopf estimate. The data are compared to analogous transitions in the rare earth region.