Observation of a second band in 94Pu239

The gamma-ray spectrum of 2.3 day Np239 has been studied with high-resolution lithium-drifted germanium spectrometers, and twelve new gamma rays of low intensity have been identified. Ten of these are characterized as the de-excitation spectrum of a K= 1 2 band based at 469.8 keV in Pu239. The decoupling parameter (a) of this band is found to be 0.48. A comparison is made of the experimental and theoretical photon relative transition intensities and reasonable agreement is obtained for the case: K 1 = 1 2 , b E1 =0 . The properties of this band are consistent with those expected for Nilsson state 1 2 − [501]. Estimates of the log ft values of Np239 beta decay to levels of the new band are made and are discussed in terms of the states involved.