The Role of Ground State Correlations in the Single-Particle Strength of Odd Nuclei with Pairing

A method based on the consistent use of the Green function formalism has been developed to calculate the distribution of the single-particle strength in odd nuclei with pairing. The method takes into account the quasiparticle-phonon interaction, ground state correlations and a "refinement" of phenomenological single-particle energies and pairing gap values from the quasiparticle-phonon interaction under consideration. The calculations for 121Sn and 119Sn that were performed in the quasiparticle$\otimes$phonon approximation, have shown a reasonable agreement with experiment. The ground state correlations play a noticeable role and mostly improve the agreement with experiment or shift the results to the right direction.Comment: 11 page

M1 Resonances in Unstable Magic Nuclei

Within a microscopic approach which takes into account RPA configurations, the single-particle continuum and more complex $1p1h\otimes phonon$ configurations isoscalar and isovector M1 excitations for the unstable nuclei ${56,78}$Ni and ${100,132}$Sn are calculated. For comparison, the experimentally known M1 excitations in ${40}$Ca and $^{208}$Pb have also been calculated. In the latter nuclei good agreement in the centroid energy, the total transition strength and the resonance width is obtained. With the same parameters we predict the magnetic excitations for the unstable nuclei. The strength is sufficiently concentrated to be measurable in radioactive beam experiments. New features are found for the very neutron rich nucleus ${78}$Ni and the neutron deficient nucleus ${100}$Sn.Comment: 17 pages (LATEX), 12 figures (available from the authors), KFA-IKP(TH)-1993-0