# Triaxial shape fluctuations and quasiparticle excitations in heavy nuclei

## TL;DR

This paper introduces a novel symmetry-conserving generator coordinate method that simultaneously considers deformation parameters and quasiparticle excitations to accurately describe spectra of various Er isotopes.

## Contribution

It is the first to incorporate deformation parameters and two-quasiparticle excitations as coordinates within a symmetry-conserving framework for nuclear structure modeling.

## Key findings

- Good agreement with experimental spectra and transition probabilities.
- Effective description of both soft and rigid nuclei.
- Unified approach for transition regions in nuclei.

## Abstract

The deformation parameters beta and gamma together with the two-quasiparticle excitations are taken into account, for the first time, as coordinates within a symmetry conserving (angular momentum and particle number) generator coordinate method. The simultaneous consideration of collective as well as single particle degrees of freedom allows us to describe soft and rigid nuclei as well as the transition region in between. We apply the new theory to the study of the spectra and transition probabilities of the 156-172Er isotopes with a Pairing plus Quadrupole residual interaction. Good agreement with the experimental results is obtained for most of the observables studied and with the same quality for the very soft and the strongly deformed nuclei.