Octupole correlations in light actinides from the interacting boson model based on the Gogny energy density functional

TL;DR

This study models quadrupole-octupole coupling in light actinides using a microscopic approach based on the Gogny energy density functional, successfully reproducing experimental spectroscopic data and highlighting octupole collectivity.

Contribution

It introduces a novel mapping of mean-field potential energy surfaces onto the Interacting Boson Model to study octupole correlations in actinides.

Findings

Good agreement with experimental Coulomb excitation data.

Pronounced octupole collectivity around $^{224}$Ra and $^{226}$Th.

Provides detailed energies and wave functions for positive- and negative-parity states.

Abstract

The quadrupole-octupole coupling and the related spectroscopic properties have been studied for the even-even light actinides $^{218-238}$Ra and $^{220-240}$Th. The Hartree-Fock-Bogoliubov approximation, based on the Gogny-D1M energy density functional, has been employed as a microscopic input, i.e., to obtain (axially symmetric) mean-field potential energy surfaces as functions of the quadrupole and octupole deformation parameters. The mean-field potential energy surfaces have been mapped onto the corresponding bosonic potential energy surfaces using the expectation value of the $sdf$ Interacting Boson Model (IBM) Hamiltonian in the boson condensate state. The strength parameters of the $sdf$-IBM Hamiltonian have been determined via this mapping procedure. The diagonalization of the mapped IBM Hamiltonian provides energies for positive- and negative-parity states as well as wave functions which are employed to obtain transitional strengths. The results of the calculations compare well with available data from Coulomb excitation experiments and point towards a pronounced octupole collectivity around $^{224}$Ra and $^{226}$Th.