The interplay between the collective dynamics of the quadrupole and octupole
deformation degree of freedom is discussed in a series of Sm and Gd isotopes
both at the mean field level and beyond, including parity symmetry restoration
and configuration mixing. Physical properties like negative parity excitation
energies, E1 and E3 transition probabilities are discussed and compared to
experimental data. Other relevant intrinsic quantities like dipole moments,
ground state quadrupole moments or correlation energies associated to symmetry
restoration and configuration mixing are discussed. For the considered
isotopes, the quadrupole-octupole coupling is found to be weak and most of the
properties of negative parity states can be described in terms of the octupole
degree of freedom alone.Comment: 31 pages, 11 figure