Influences of α -clustering configurations on the giant dipole resonance in hot compound systems

The influences of $\ensuremath{\alpha}$-clustering configurations on the giant dipole resonance (GDR) in hot compound systems are discussed under the framework of an extended quantum molecular dynamics (EQMD) model. The computed GDR spectra in the hot nucleus $^{28}\mathrm{Si}$ are split into two peaks which are very consistent with the experimental measurement and are remarkably sensitive to the configurations of projectile $^{16}\mathrm{O}$, including the linear chain, kite, square, and tetrahedron configurations. Meanwhile, the sensitivity of the GDR lineshapes to the configurations of $^{16}\mathrm{O}$ gradually increases with angular momentum. However, for the fusion system induced by $^{20}\mathrm{Ne}$, their GDR lineshapes in $^{47}\mathrm{V}$ and $^{32}\mathrm{S}$ are mostly independent of the $\ensuremath{\alpha}$-clustering configurations compared with those in the hot compound systems induced by the projectile $^{16}\mathrm{O}$, which may be attributed to their much more similar geometric structures between the square pyramid and trigonal bipyramid configurations in $^{20}\mathrm{Ne}$. Additionally, we find that the GDR lineshapes in hot compound systems are sensitive to the geometric distributions of the projectile in phase space when it is compared to those with Woods-Saxon distribution and polarization in projectiles. These results demonstrate that the GDR can be taken as an experimental observable to extract information about the configurations of reaction systems.