Dipole excitation of $^6$Li and $^9$Be studied with an extended quantum molecular dynamics model

TL;DR

This study investigates giant dipole resonance excitations in light nuclei $^{6}$Li and $^{9}$Be using an extended quantum molecular dynamics model, revealing clustering effects and resonance structures related to their internal configurations.

Contribution

It introduces a detailed analysis of GDR spectra in light nuclei considering clustering structures within an extended quantum molecular dynamics framework, highlighting the role of alpha clustering.

Findings

GDR peak around 31 MeV for $^{6}$Li due to alpha clustering

Lower energy pygmy dipole resonance linked to cluster interactions

Mixed configurations explain GDR features in $^{9}$Be

Abstract

The $\alpha$ ($^4$He) - clustering structure is a common phenomenon in light nuclei due to the decreasing contribution of mean field in few-body system. In this work we presented calculations of giant dipole resonance (GDR) excitations for two non $\alpha$-conjugate light nuclei, namely $^{6}$Li and $^{9}$Be, within a framework of an extended quantum molecular dynamics model. For $^{6}$Li, we investigated the GDR spectra from the two-body clustering structure with $\alpha$ + deuteron as well as the three-body structure with $\alpha$ + $n$ + $p$, and found that the major $\alpha$-clustering contribution on the GDR peak is located at around 31 MeV, while the resonance contributions between clusters, namely $\alpha$ and deuteron or ($n$ + $p$), are located on the lower energy side, which can be regarded as pygmy dipole resonance (PDR). For $^{9}$Be, a mixture configuration contribution for the Chain-like structure and Borromean-like structure of the $\alpha$ + n + $\alpha$ configuration can somehow explain its GDR results.