Studies of the Giant Dipole Resonance in $^{27}$Al, $^{40}$Ca, $^{56}$Fe, $^{58}$Ni and $^{208}$Pb with high energy-resolution inelastic proton scattering under 0$^\circ$

TL;DR

This study investigates the fine structure of the Isovector Giant Dipole Resonance in several nuclei using high-resolution inelastic proton scattering at 0°, revealing detailed resonance features and comparing results with theoretical models.

Contribution

It provides new high-resolution measurements of the IVGDR in multiple nuclei and applies wavelet analysis to extract characteristic energy scales, enhancing understanding of giant resonance decay mechanisms.

Findings

Observation of fine structure in IVGDR across nuclei

Extraction of characteristic energy scales via wavelet analysis

Agreement of photoabsorption cross sections with previous photon-based data

Abstract

A survey of the fine structure of the Isovector Giant Dipole Resonance (IVGDR) was performed, using the recently commissioned zero-degree facility of the K600 magnetic spectrometer at iThemba LABS. Inelastic proton scattering at an incident energy of 200 MeV was measured on $^{27}$Al, $^{40}$Ca, $^{56}$Fe, $^{58}$Ni and $^{208}$Pb. A high energy resolution ($\rm{\Delta}\it{E} \simeq$ 40 keV FWHM) could be achieved after utilising faint-beam and dispersion-matching techniques. Considerable fine structure is observed in the energy region of the IVGDR and characteristic energy scales are extracted from the experimental data by means of a wavelet analysis. The comparison with Quasiparticle-Phonon Model (QPM) calculations provides insight into the relevance of different giant resonance decay mechanisms. Photoabsorption cross sections derived from the data assuming dominance of relativistic Coulomb excitation are in fair agreement with previous work using real photons.