Evidence for rotational to vibrational evolution along the yrast line in the odd-A rare-earth nuclei

TL;DR

This study investigates the evolution from rotational to vibrational nuclear structures along the yrast line in odd-A rare-earth nuclei, using E-GOS curves and TRS model calculations to reveal shape changes at high spins.

Contribution

It introduces the use of E-GOS curves to identify rotational-vibrational evolution and applies TRS calculations to analyze shape stability in odd-A rare-earth nuclei.

Findings

Evidence of rotation to vibration transition along the yrast line.

Identification of shape changes at high spin states.

Stable prolate shapes at low spins with deformation decrease at higher spins.

Abstract

The phase transition of nuclei to increasing angular momentum (or spin) and excitation energy is one of the most fundamental topics of nuclear structure research. The odd-N nuclei with A equal 160 are widely considered belonging to the well-deformed region, and their excitation spectra are energetically favored to exhibit the rotational characteristics. In the present work, however, there is evidence indicating that the nuclei can evolve from rotation to vibration along the yrast lines while increasing spin. The simple method, named as E-Gamma Over Spin (E-GOS) curves, would be used to discern the evolution from rotational to vibrational structure in nuclei as a function of spin. In addition, in order to get the insight into the rotational-like properties of nuclei, theoretical calculations have been performed for the yrast bands of the odd-A rare-earth nuclei using the total Routhian surfaces (TRS) model. The TRS plots indicate that the 165Yb and 157Dy isotopes have stable prolate shapes at low spin states. At higher rotational frequency (larger than 0.50 MeV), a distinct decrease in the quadrupole deformation is predicted by the calculations, and the isotopes becomes rigid in the gamma deformation.