Origin of fine structure of the giant dipole resonance in sd-shell nuclei

TL;DR

This study combines high-resolution proton scattering data and advanced RPA calculations to explore the fine structure of the GDR in sd-shell nuclei, revealing deformation and alpha clustering as key factors.

Contribution

It introduces a realistic RPA approach with Argonne V18 interaction and wavelet analysis to explain GDR fragmentation in sd-shell nuclei.

Findings

Good agreement between data and calculations supports deformation origin.

Fine structure scales are characterized by wavelet analysis.

Alpha clustering influences GDR fragmentation.

Abstract

A set of high resolution zero-degree inelastic proton scattering data on 24Mg, 28Si, 32S, and 40Ca provides new insight into the long-standing puzzle of the origin of fragmentation of the Giant Dipole Resonance (GDR) in sd-shell nuclei. Understanding is provided by state-of-the-art theoretical Random Phase Approximation (RPA) calculatios for deformed nuclei using for the first time a realistic nucleon-nucleon interaction derived from the Argonne V18 potential with the unitary correlation operator method and supplemented by a phenomenological three-nucleon contact interaction. A wavelet analysis allows to extract significant scales both in the data and calculations characterizing the fine structure of the GDR. The fair agreement supports that the fine structure arises from ground-state deformation driven by alpha clustering.