Octupole and hexadecapole deformations in atomic nuclei

Kosuke Nomura (Hokkaido University, Japan)

This presentation highlights recent theoretical studies on the octupole and hexadecapole correlations, and related collective excitations in medium-heavy and heavy nuclei within the mapped interacting boson model, in which the bosonic Hamiltonian giving rise to low-energy spectra and electromagnetic transition rates for a given nucleus is determined by using as inputs the self-consistent mean-field calculations based on a universal energy density functional. Octupole correlations are shown to be present in a number of nuclei with mass A=70-250, including the well known cases of actinides, rare-earth, and lanthanides with nucleons numbers close to 56, 88, and 136, and some N~Z~34 nuclei, in which triaxiality and coexistence of quadrupole shapes also play a crucial role. The inclusion of hexadecapole degree of freedom in the model is shown to improve descriptions of positive-parity states in both nearly spherical and deformed rare-earth nuclei, and produce hexadecapole bands exhibiting large E4 transitions to the ground state.