The impact of hexadecapole correlations on the low-energy spectroscopic properties of Th, U, and Pu nuclei, within the mass range $232\le A\le 240$, is studied systematically using the mapped $sdg$-IBM model. Fermionic input is obtained via the quadrupole-hexadecapole constrained Hartree-Fock-Bogoliubov approximation, based on the parametrization D1S of the Gogny energy density functional. The $sdg$-IBM Hamiltonian parameters are determined by mapping the quadrupole-hexadecapole fermionic mean-field potential-energy surfaces onto the corresponding bosonic surfaces. The low-energy spectra and transition strengths, obtained via the diagonalization of the $sdg$-IBM Hamiltonian, compare well with the available experimental data. It is shown that the effects of hexadecapole collectivity can be observed in high-spin yrast states with spins $J^{\pi }⩾{10}^{+}$. The mapped $sdg$-IBM improves the excitation energies of those states, as compared with the simpler $sd$-IBM model. The $sdg$-IBM also improves the description of the $E2$ transition strengths between high-spin yrast states and predicts strong $E4$ transitions from nonyrast $4^{+}$ states to the $0^{+}$ ground state.

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• Collective levels
• Electromagnetic transitions
• Energy levels
• Nuclear shapes and moments
• Nuclear structure & decays
• Nucleon distribution
• A ≥ 220
• Models based on symmetries
• Nuclear density functional theory