Deformation dependence of the isovector giant dipole resonance: The neodymium isotopic chain revisited

TL;DR

This study investigates how nuclear deformation affects the isovector giant dipole resonance in neodymium isotopes, revealing shifts in resonance energies and asymmetries related to shape phase transitions, supported by experimental data and RPA calculations.

Contribution

It provides new experimental data on IVGDR shapes across a chain of neodymium isotopes and compares these with theoretical RPA models, highlighting deformation effects.

Findings

Resonance maxima shift to higher energies in vibrational and transitional nuclei.

Deformed nuclei show asymmetric cross sections instead of double-hump structures.

RPA calculations with SLy6 force effectively describe the observed IVGDR shapes.

Abstract

Proton inelastic scattering experiments at energy E_p = 200 MeV and a spectrometer scattering angle of 0 degree were performed on 144,146,148,150Nd and 152Sm exciting the IsoVector Giant Dipole Resonance (IVGDR). Comparison with results from photo-absorption experiments reveals a shift of resonance maxima towards higher energies for vibrational and transitional nuclei. The extracted photo-absorption cross sections in the most deformed nuclei, 150Nd and 152Sm, exhibit a pronounced asymmetry rather than a distinct double-hump structure expected as a signature of K-splitting. This behaviour can be related to the proximity of these nuclei to the critical point of the phase shape transition from vibrators to rotors with a soft quadrupole deformation potential. Self-consistent random-phase approximation (RPA) calculations using the SLy6 Skyrme force provide a relevant description of the IVGDR shapes deduced from the present data