Clustering in Stable and Exotic Light Nuclei

Abstract

Since the pioneering discovery of molecular resonances in the 12 C+ 12 C reaction more than half a century ago a great deal of research work has been undertaken in alpha clustering. Our knowledge on physics of nuclear molecules has increased considerably and nuclear clustering remains one of the most fruitful domains of nuclear physics, facing some of the greatest challenges and opportunities in the years ahead. The occurrence of "exotic" shapes and Bose-Einstein alpha condensates in light N =Z alpha-conjugate nuclei is investigated. Various approaches of the superdeformed and hyperdeformed bands associated with quasimolecular resonant structures are presented. Evolution of clustering from stability to the drip-lines is examined: clustering aspects are, in particular, discussed for light exotic nuclei with large neutron excess such as neutron-rich Oxygen isotopes with their complete spectroscopy. * Review

Recent Experimental Results on Nuclear Cluster Physics

“…In light α-like nuclei clustering is observed as a general phenomenon not only at high excitation energies close to the α-decay thresholds [6,8,17,20] but may also play a key role at low excitation energies and for the ground states. This exotic behavior was perfectly illustrated by the famous "Ikedadiagram" for N =Z nuclei in 1968 [21], which was modified and recently extended by von Oertzen [22,23] for neutron-rich nuclei, as shown in the right panel of Fig.…”

“…Among the greatest challenges in nuclear science was the understanding of the clustered structure of nuclei from both the experimental and theoretical perspectives [1,2,3,4,5,6,7,8]. Progress in physics of nuclear molecules and nuclear clustering were facing some of the greatest challenges and opportunities in the years ahead.…”

“…1 (taken from the cover of Ref. [14]) summarizes the different types of clustering that were discussed during the last two or three decades [8,15]. Most of these exotic structures were investigated in an experimental context by using either some new approaches or developments of older methods [16].…”

“…Starting in the 1960s the search for resonant structures in the excitation functions for various combinations of light α-conjugate (N =Z) nuclei in the energy regime from the Coulomb barrier up to regions with high excitation energies (E x =20−50 MeV) remains a subject of contemporary debate [1,8]. These resonances were interpreted in terms of nuclear molecules [1].…”

“…The question of how quasimolecular resonances may reflect continuous transitions from scattering states in the ion-ion potential to true cluster states in the compound systems was still unresolved in the 1990s [1]. In many cases, these resonant structures were associated with strongly-deformed shapes and with α-clustering phenomena [6,8,17,18], predicted from the Nilsson-Strutinsky approach, the cranked α-cluster model [6,17], or other mean-field calculations [18,19].…”