Interference effect of doorway states in a radiative capture reaction

This work investigates the interference in radiative nucleon capture reactions between the giant resonances and the doorway configurations mixed in compound nucleus levels. A unified formalism has been established by which it is possible to study the interference among the four parts in the capture amplitude: the potential capture, valence capture, semidirect capture, and fine resonance capture stemming from doorway configurations. The ¹²C(p,γ₀) data in the excitation energy region of 10–30 MeV in ¹³N were analyzed by means of this formalism with an emphasis on investigating the dips and peaks superimposed on the pigmy resonance. These structures are interpreted as destructive or constructive interferences in doorway configurations. Parameters for both the giant resonances and fine levels were extracted by fitting the measured data. We extend the study to discuss the potential of observing similar interferences in the reactions ¹²C(n,γ₀) and ¹²C(p,γ_n)¹³N^*, leading to excited states of the final nucleus.