Quadrupole-phonon models and a cluster-vibration model for nuclei in the mass region 50-150

A systematic approach to even-even, odd-even and odd-odd nuclei, based on spherical quadrupole phonons, is presented. In the truncated quadrupole-phonon model (TQM), no explicit shell-model degrees of freedom appear and the model is based on SU(6) symmetry. In the particle-truncated quadrupole-phonon model (PTQM) an odd single particle is coupled to the TQM core. In the cluster-vibration model (CVM), a few selected shell-model degrees of freedom (a cluster) are coupled to quadrupole vibrations (harmonic or TQM). In this way, even-even, odd-even and odd-odd nuclei are described on an equal footing. In the quasi-cluster-vibration model (QCVM), a cluster consists of a few BCS quasi-particles with particle-number projection. (author)