An RPA model for the description of one-nucleon emission processes and application to 16O(γ, N) reactions

A coordinate space RPA formalism is proposed to handle one-nucleon emission processes in a self-consistent way. A method is outlined to solve the RPA equations so obtained for the whole class of rotationally invariant effective interactions, including those having a velocity dependence. The method is used to study ¹⁶O(γ, N) reactions with Skyrme-type effective interactions. The use of the long-wavelength approximation (LWA) when handling reactions of this type at medium energies, is criticized. Different alternative forms for the electric transition operators are used, applying Siegert's theorem or not, and it is shown that at higher momentum transfer, the obtained results are strongly sensitive to it. We emphasize that especially beyond energy regions where the LWA is valid, the use of Siegert's theorem should be carefully examined.