Exotic nuclear shape due to cluster formation at high angular momentum

It is shown, for the first time, how the exotic shapes due to cluster formation at high excitation energy and angular momentum are manifested through giant dipole resonance (GDR) strength function under the framework of the extended quantum molecular dynamics (EQMD) model. The results of EQMD calculation are compared with the existing experimental data of S-32 and Si-28 formed in the reactions Ne-20+C-12 and O-16+C-12, respectively, at high angular momenta. It is found that the EQMD predicts the general trend of the experimental GDR strength functions for S-32 and Si-28 by considering the ring or toroidal configuration, whereas the linear chain configurations with alpha clusters can reproduce the higher-energy peak in S32 and Si28. Thus, the direct signature of the cluster formation at high temperature and angular momentum is the observation of a GDR peak approximate to 25MeV which cannot be predicted within the mean-field calculations. The present result highlights the role of alpha cluster states above the decay threshold, which is still an open field of investigation.