Observation of resonances in {sup 239}Pu (n,{alpha}) 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 {sup 239}Pu target. The analysis of the data showed a set of previously unknown resonances identified as arising from a (n,{alpha}) reaction channel. These resonances differ from the known fission and radiative capture resonances in {sup 239}Pu and do not correspond to any known capture resonances from structural material around the {sup 239}Pu target assembly. The new resonances decay uniquely via {alpha}-emission, and represent new states not explained by current models. The yield of the observed (n,{alpha}) reaction channel is 60 {+-} 5 times as strong as the fission channel, as determined from the high-energy {alpha}-particle and fission fragment peak area observed in the Si detectors.