Microscopic description of the shape coexistence in the A ∼ 70 mass region

The shape-coexistence phenomena dominating the structure of the nuclei in the A ∼ 70 mass region are investigated within different approaches using general symmetry-projected Hartree-Fock-Bogolyubov configurations as basic building blocks, a rather large model space, and a suitably defined effective two-body interaction. The selection of the relevant configurations determines the dynamics of the considered system in the framework of the Excited Vampir and Excited Fed Vampir variational procedures involving real or complex mean fields. The results concerning the structure of low- and high-spin states in a number of even-even Ge, Se, and Kr nuclei indicate that a variable mixing of more or less deformed prolate and oblate quasiparticle determinants is responsible for the complex behavior of the doubly even nuclei in this mass region. 51 refs., 5 figs., 26 tabs