Rapid structural change in low-lying states of neutron-rich Sr and Zr isotopes

TL;DR

This study investigates the rapid shape transition in neutron-rich Sr and Zr isotopes by combining collective Hamiltonian models with mean-field calculations, revealing a shape evolution from spherical to prolate forms around N=60.

Contribution

It introduces a comprehensive approach using relativistic and non-relativistic mean-field models to explain shape transitions in neutron-rich isotopes.

Findings

Shape transition from spherical to oblate and prolate observed

Predictions align with experimental data for isotope shifts and transition strengths

Different force models show varying degrees of shape change around N=60

Abstract

The rapid structural change in low-lying collective excitation states of neutron-rich Sr and Zr isotopes is tudied by solving a five-dimensional collective Hamiltonian with parameters determined by both relativistic mean-field and non-relativistic Skyrme-Hartree-Fock calculations using the PC-PK1 and SLy4 forces respectively. Pair correlations are treated in BCS method with either a separable pairing force or a density-dependent zero-range force. The isotope shifts, excitation energies, electric monopole and quadrupole transition strengths are calculated and compared with corresponding experimental data. The calculated results with both the PC-PK1 and SLy4 forces exhibit a picture of spherical-oblate-prolate shape transition in neutron-rich Sr and Zr isotopes. Compared with the experimental data, the PC-PK1 (or SLy4) force predicts a more moderate (or dramatic) change in most of the collective properties around N=60. The underlying microscopic mechanism responsible for the rapid transition is discussed.