Clustering Aspects of Highly Excited States and Neutron-Rich Nuclei

Abstract

Recent researches of clustering aspects in stable and unstable nuclei based on antisymmetrized molecular dynamics (AMD) are reported. We will focus on the clustering of highly excited states of 24 Mg, the low-lying spectroscopy and novel exotic clustering in the vicinity of the island of inversion. §1. IntroductionClustering aspect is one of the most important ingredients of the nuclear manybody problem. It embodies the dynamical aspects of nuclear system, namely assembling and disassembling of nucleons, which make nuclear physics challenging and fascinating problem. Owing to the theoretical and experimental developments, the domain of the cluster studies is rapidly expanding toward highly excited and neutron-rich nuclei. For example, the studies of unstable nuclei have revealed novel types of clustering represented by Be isotopes, 1)-3) and analogous structures have been discussed in heavier system. 4), 5) The intensive discussions on the nα gas-like state in 12 C 6) and 16 O 7) renewed our interest in the clustering of the highly excited states. Theoretical and experimental studies are rapidly developing toward heavier systems.AMD has been one of powerful theoretical approaches to investigate those clustering aspects in the highly excited states and in the neutron-rich nuclei. In this article, we report some of recent activities of AMD studies for clustering of stable and unstable nuclei. The dominance of the cluster states around the threshold energies despite of the mean-field nature of the low-lying states is remarked using 24 Mg 8) as an illustrative example ( §3). AMD has achieved sufficient accuracy and predictive power for the study of the low-lying mean-field dynamics in heavier unstable nuclei. It enabled us to discuss and predict the coexistence of the spherical and deformed states 9) and neutron-halo structure 10), 11) in the island of inversion ( §4). Clustering will also play an important role in the vicinity of the island of inversion. We predict the coexistence of the mean-field states and the novel types of clustering which are composed of clusters and many valence neutrons at small excitation energies in F isotopes far from stability. 12)

Resonances with triaxial deformation in the complex scaled Green’s function method

“…There are several islands of axial asymmetry on the nuclear chart, and most of them turn out to be triaxially deformed in their ground states [3]. This breaking phenomenon of axial symmetry is attracting more attention than before, with research in topics such as nuclear dynamical properties [4], the increase of the binding of nucleons [3], the loss of traditional magic numbers [5], shape coexistence [6], and so on. Although the triaxial nuclei cannot be measured directly, nuclear wobbling [7] and chiral bands [8,9] have been used to infer the existence of triaxiality in the past decades.…”

“…Although the triaxial nuclei cannot be measured directly, nuclear wobbling [7] and chiral bands [8,9] have been used to infer the existence of triaxiality in the past decades. For exploring triaxiality, a series of models and methods have been established, including the five-dimensional collective Hamiltonian (5DCH) theory [10], the cranked Woods-Saxon (WS) shell model [11], the antisymmetrized molecular dynamics (AMD) combined with the generator coordinate method (GCM) [5], and so on.…”

“…This can help us better understand the energy level structure to obtain the nuclear properties. Since deformed structures have had a profound effect on the development of nuclear physics, we apply the CGF method to the triaxially deformed nucleus 43 S [5], which is characterized by the quadrupole deformation parameters β and γ.…”