Shape coexistence and low-lying collective states in A #approx #100 Zr nuclei

Collective quadrupole and octupole excitations in even 94-00Zr nuclei are studied within the fully microscopic generator-coordinate method using a basis generated by the selfconsistent Hartree-Fock BCS method. Results with the effective interaction SkM* correctly describe the experimentally observed spherical to deformed shape transition at A=100. Properties of low-lying 0+, 2+ and 3- states are analysed. The measured B(E3) value of 65 single-particle units in 96Zr is underestimated in our calculations. Various aspects of our theoretical approach are discussed, including Skyrme force parametrization, treatment of pairing and one- versus two-dimensional description of octupole excitations. (orig.)