Pygmy and Giant Dipole Resonances by Coulomb Excitation using a Quantum Molecular Dynamics model

TL;DR

This study investigates Pygmy and Giant Dipole Resonances in Ni isotopes using Coulomb excitation within the IQMD model, analyzing their spectral properties and sensitivities to nuclear symmetry energy, providing constraints for the model.

Contribution

It introduces a detailed analysis of PDR and GDR using Coulomb excitation in the IQMD framework, including their dependence on nuclear symmetry energy and neutron excess.

Findings

GDR and PDR spectra are successfully calculated and characterized.

The energies and strengths of resonances are sensitive to the symmetry energy term.

The PDR strength increases linearly with neutron excess.

Abstract

Pygmy and Giant Dipole Resonance (PDR and GDR) in Ni isotopes have been investigated by Coulomb excitation in the framework of the Isospin-dependent Quantum Molecular Dynamics model (IQMD). The spectra of $\gamma$ rays are calculated and the peak energy, the strength and Full Width at Half Maximum (FWHM) of GDR and PDR have been extracted. Their sensitivities to nuclear equation of state, especially to its symmetry energy term are also explored. By a comparison with the other mean-field calculations, we obtain the reasonable values for symmetry energy and its slope parameter at saturation, which gives an important constrain for IQMD model. In addition, we also studied the neutron excess dependence of GDR and PDR parameters for Ni isotopes and found that the energy-weighted sum rule (EWSR) $PDR_{m_1}/GDR_{m_1}%$ increases linearly with the neutron excess.