Neutron-proton collective motion. I. Nuclear shapes

The rich variety of possible quadrupole shapes in proton-neutron systems are explored. New shape parameters are introduced that serve to simplify the expression for the energy surface of the general Hamiltonian and that allow a systematic classification of the different configurations into distinct families. Both axial and non-axial, aligned and non-aligned deformed shapes are examined. Particular attention is paid to new features (e.g., oblique shapes) that occur.