Triaxial projected shell model study of gamma-vibrational bands in even-even Er isotopes

TL;DR

This paper extends the triaxial projected shell model to include multi-quasiparticle states, enabling detailed high-spin studies of gamma-vibrational bands in Er isotopes with good agreement to experimental data.

Contribution

It introduces a new basis in the shell model to study high-spin gamma-vibrational bands in Er isotopes, including predictions for bands with multiple gamma phonons.

Findings

Gamma-bands in neutron-deficient Er isotopes are close to the yrast band.

Predicted near-degeneracy of gamma-bands and yrast bands at high spins.

Model shows good agreement with experimental data for known states.

Abstract

We expand the triaxial projected shell model basis to include triaxially-deformed multi-quasiparticle states. This allows us to study the yrast and gamma-vibrational bands up to high spins for both gamma-soft and well-deformed nuclei. As the first application, a systematic study of the high-spin states in Er-isotopes is performed. The calculated yrast and gamma-bands are compared with the known experimental data, and it is shown that the agreement between theory and experiment is quite satisfactory. The calculation leads to predictions for bands based on one- and two-gamma phonon where current data are still sparse. It is observed that gamma-bands for neutron-deficient isotopes of 156Er and 158Er are close to the yrast band, and further these bands are predicted to be nearly degenerate for high-spin states.