Orateur
Description
Different kinds of shape deformations may simultaneously manifest in certain regions of the nuclear chart entailing corresponding collective modes and specific structure of excitation spectra. In particular, in the mass region of Barium, Cerium, Neodymium and Samarium isotopes one may observe different degrees of manifestation of pear-shape quadrupole-octupole (reflection-asymmetric) modes, either stiff, e.g. in $^{144,146}$Ba, or soft in other nuclei and, at the same time, manifestation of quadrupole triaxiality, again, soft or stiff enough to form chiral structures in the spectrum, such as, e.g., in $^{136}$Nd. In this talk we address the manifestation of reflection-asymmetric degrees of freedom in coexistence with triaxial quadrupole modes. We discuss the possibility for the presence of non-axial octupole deformation and the way to identify it in the structure of alternating-parity spectra by using a collective quadrupole-octupole rotation model. We show that the possible appearance of triaxial modes may stronger affect the higher angular momenta by counteracting the parity-shift effect with a simultaneous stabilization of the overall quadrupole-octupole shape.
