Investigating the ( n , γ f ) Reaction as a Way of Studying the Properties of Transitions between Highly Excited States in Heavy Nuclei

The history and current status of investigations of the unique two-step ( n , γ f ) reaction observed in heavy nuclei under the influence of neutrons are discussed using the example of measurements made on the neutron time-of-flight spectrometer GNEIS in Gatchina. It is shown what is already known and what kind of information can be derived from experiments to study the ( n , γ f ) reaction on resonance neutrons for the most important fissionable nuclei 235 U and 239 Pu, including information on the properties of primary gamma transitions between highly excited states near the neutron bonding energy.