We present results from large-scale shell-model calculations of even and odd tin isotopes from 134Sn to 142}Sn with a shell-model space defined by the 1f7/2,2p3/2,0h9/2,2p1/2,1f5/2,0i13/2 single-particle orbits. An effective two-body interaction based on modern nucleon-nucleon interactions is employed. The shell-model results are in turn analyzed for their pairing content using a generalized seniority approach. Our results indicate that a pairing-model picture captures a great deal of the structure and the correlations of the lowest lying states for even and odd isotopes.Comment: 7 pages, revtex latex style, submitted to PR

This review aims at a critical discussion of the interplay between effective interactions derived from various manybody approaches and spectroscopic data extracted from large scale shell-model studies. To achieve this, our many-body scheme starts with the free nucleon-nucleon (NN) interaction, typically modelled on various meson exchanges. The NN interaction is in turn renormalized in order to derive an effective medium dependent interaction. The latter is in turn used in shell-model calculations of selected nuclei. We also describe how to sum up the parquet class of diagrams and present initial uses of the effective interactions in coupled cluster many-body theory.

We propose a scheme for extracting an effective three-body interaction originating from a two-nucleon interaction. This is based on theQ-box method of Kuo and collaborators, where folded diagrams are obtained by differentiating a sum of nonfolded diagrams with respect to the starting energy. To gain insight we have studied several examples using the Lipkin model where the perturbative approach can be compared with exact results. Numerically the three-body interactions can be significant and in a matrix example good accuracy was not obtained simultaneously for both eigenvalues with two-body interactions alone.

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In the framework of the Alpha Cluster Model extended calculations of form factors of elastic and inelastic [Formula: see text] and [Formula: see text] (7.66 MeV) electron scattering on 12C were performed. Two possible alpha cluster configurations (linear and triangular) were considered for states assigned to different rotational bands and although the configuration mixture was found to be important for explanation of the inelastic monopole form factor, a fully consistent picture, including all available data, was not obtained.