Recent progress in nuclear clustering

The study of nuclear clustering lies at the frontier of nuclear physics, providing key insights into effective nuclear interactions and the development of nuclear structure theories. It also plays a crucial role in advancing our understanding of nuclear astrophysical processes, heavy-ion collisions, and the properties of neutron-rich matter. Over the past decade, we have continuously advanced our detection techniques—most notably through the development of large charged-particle telescope arrays—and conducted systematic experimental investigations of cluster structures across a broad range of contexts using both domestic and international nuclear physics facilities, leading to a series of significant breakthroughs. In this review, we first outline the primary experimental methods for exploring clustering phenomena, including approaches for studying the cluster structure of excited states and knockout-reaction-based techniques for probing clustering in the ground state. We then summarize our recent progress, highlighting molecular structures in the excited states of 10,12Be studied by measuring the selective cluster decay, linear-chain molecular states in 14,16C, Bose–Einstein condensate (BEC)-like cluster states in 16O, the dineutron-condensate cluster state in 8He probed by measuring the characteristic transition strength and emission of correlated neutron pairs, and surface α-clustering in heavy nuclei probed by using the quasi-free (p, pα) reaction. We also present a brief outlook on future directions in this field. Molecular cluster structures and BEC-like α-condensate states are expected to remain central themes of theoretical and experimental studies in the coming decade. With continued advances in RIB facilities and experimental techniques, studies of molecular cluster structures are anticipated to extend to heavier systems such as O and Ne, while searches for α-condensate states involving more α clusters—for example, 5α condensate in 20Ne and 6α condensate in 24Mg—are actively underway. Quasi-free (p, pα) cluster knockout reactions are being applied to unstable nuclei, and dedicated detector arrays for such measurements are now under development. These cluster knockout studies are also being extended to other clusters (d,t,3He), aiming for a comprehensive understanding of cluster formation in both finite nuclei and infinite nuclear matter. Significant progress has been made in the study of neutron correlations and clusters, but many open questions remain, with a prominent example being the elusive tetraneutron. Future experiments should go beyond resonance energies and widths, and probe internal neutron correlations of multi-neutron systems by directly detecting the decay neutrons. It is of great interest to consider neutron clusters accommodated in a nuclear environment, such as in neutron-rich nuclei, where the neutron correlations will be enhanced. Under such conditions, multiple dineutron clusters may form and further develop into condensate-like cluster states. From an experimental perspective, neutron detector arrays with high resolution and high efficiency for the detection of multiple neutrons are essential, and a new multi-neutron detector array is currently under development in our laboratory.