Fragmentation of single-particle strength in spherical open-shell nuclei: Application to the spectral functions in 142Nd

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.