Observation of resonances in 239Pu (n,α) reactions

A measurement performed at the Argonne National Laboratory (ANL) Intense Pulsed Neutron Source (IPNS) facility studied the incident neutron energy-dependent charged particle and fission fragment yields from a 239Pu target. The analysis of the data showed a set of previously unknown resonances identified as arising from a (n,α) reaction channel. These resonances differ from the known fission and radiative capture resonances in 239Pu and do not correspond to any known capture resonances from structural material around the 239Pu target assembly. The new resonances decay uniquely via α-emission, and represent new states not explained by current models. The yield of the observed (n,α) reaction channel is 60 ± 5 times as strong as the fission channel, as determined from the high-energy α-particle and fission fragment peak area observed in the Si detectors