IBM-1 description of the fission products $^{108,110,112}$Ru

TL;DR

This paper uses IBM-1 calculations to analyze the nuclear structure of Ru isotopes, comparing different Hamiltonian models to experimental data and exploring their relation to triaxial rotor models.

Contribution

It introduces a Hamiltonian with three-body terms to better describe Ru isotopes and examines the connection between IBM and triaxial rotor models.

Findings

Good agreement with experimental energies and B(E2) ratios

Three-body terms improve odd-even staggering description

IBM relates closely to the triaxial rotor model

Abstract

IBM-1} calculations for the fission products $^{108,110,112}$Ru have been carried out. The even-even isotopes of Ru can be described as transitional nuclei situated between the U(5) (spherical vibrator) and SO(6) ($\gamma$-unstable rotor) symmetries of the Interacting Boson Model. At first, a Hamiltonian with only one- and two-body terms has been used. Excitation energies and $B$(E2) ratios of gamma transitions have been calculated. A satisfactory agreement has been obtained, with the exception of the odd-even staggering in the quasi-$\gamma$ bands of $^{110,112}$Ru. The observed pattern is rather similar to the one for a rigid triaxial rotor. A calculation based on a Hamiltonian with three-body terms was able to remove this discrepancy. The relation between the IBM and the triaxial rotor model was also examined.