D. Van Neck

A method is presented for the calculation of single-particle strength distributions in spherical semi-magic open-shell nuclei. The model is based upon the equation-of-motion method and differs from the standard quasiparticle-phonon model in that also backward-going terms are included in the self-energy of the nucleons. In the limit to closed shells the model reduces to the microscopic particle-vibration method with RPA-like polarization propagators. The model is applied to the proton particle and hole spectral functions in the odd nuclei adjacent to ¹⁴²Nd.

We present a new method to describe the fragmentation of single-particle strength in the framework of the Green function formalism. By means of an iterative scheme, we are able to construct a self-consistent solution of the Dyson equation up to second order in the interaction. Damping effects, such as the broadening of the spectral function for deep-lying hole states, show up in a natural way. We apply the formalism to a schematic model and to the case of the doubly-closed shell nucleus ⁴⁸Ca.

We present results of self-consistent Hartree-Fock (HF) and continuum random-phase-approximation (RPA) calculations for proton emission following the electro-excitation of 58Ni in the energy range ω = 25–42 MeV. The calculations are performed for four different values of the momentum transfer ranging between 0.4 and 0.8 fm⁻¹. For the above kinematics, an extensive amount of data is available. We confront the data with the theoretical results obtained within the plane-wave impulse approximation (PWIA), HF and RPA. The role of the final-state interaction (FSI) is investigated. Furthermore, we investigate in how far the angular distributions may reflect the occurrence of giant resonances. A quasi-free knockout (QFK) reaction picture is found unable to account for details of the data. Although the RPA offers a reasonable description of the overall q and ω behaviour of the angular distributions, it does not provide a good description of the proton-decay branch of the quadrupole and octupole resonance.

We present self-consistent Hartree-Fock (HF) and random-phase approximation (RPA) calculations for quasi-elastic ¹⁶O(e, e′ p) cross sections. The role of the final state interaction (FSI) and RPA-like multi-step processes is discussed. Comparing the results with the experimental data, spectroscopic factors could be derived. It is found that the RPA correlations systematically enhance the deduced spectroscopic factors.