Interactions in between nucleons develop different interesting nuclear structures, varying from round to warped nuclei and even neutron halos with sporadic surface area density. The introduction of cluster structures within these formations is a fascinating phenomenon.
Groundbreaking research study by the Institute of Modern Physics exposes molecular-type structures in the ground state of atomic nuclei, providing speculative proof for a decades-old hypothesis and opening new courses in nuclear physics research.
A pivotal research study by scientists at the Institute of Modern Physics has revealed molecular-type structures in atomic nuclei, changing our understanding of nuclear matter.
Researchers from the Institute of Modern Physics (IMP) of the Chinese Academy of Sciences (CAS), along with their collaborators, have actually just recently discovered a molecular-type structure in the ground state of atomic nuclei. The research study was published in Physical Review Letters and highlighted as a “Featured in Physics” post.
Comprehending the Atomic Nucleus
The atomic nucleus, a quantum many-body system composed of neutrons and protons, is exceptionally small (just about one-ten-thousandth the size of an atom), but it houses over 99.9% of an atoms total mass. Interactions between nucleons produce various intriguing nuclear structures, varying from spherical to warped nuclei and even neutron halos with sporadic surface density. The development of cluster structures within these developments is a fascinating phenomenon.
Cluster structures are rarely seen in the ground state of atomic nuclei. Discussions on ground-state cluster structures can be traced back to 1938 when theoretical physicists, through the analysis of binding energies in α-conjugate nuclei, suggested the possible existence of α-molecule-like cluster structures in the ground states of nuclei such as oxygen-16, beryllium-8, and carbon-12. The α-clusters bound within beryllium-10 nuclei were knocked out by protons– with nearly no momentum transferred to the residual nucleus– therefore maintaining information about the cluster structure in the ground state of beryllium-10.
Schematic view of the cluster knockout reaction in inverted kinematics. Credit: LI Pengjie
The Significance of Cluster Structures
Cluster structures are seldom seen in the ground state of atomic nuclei. Discussions on ground-state cluster structures can be traced back to 1938 when theoretical physicists, through the analysis of binding energies in α-conjugate nuclei, recommended the possible presence of α-molecule-like cluster structures in the ground states of nuclei such as beryllium-8, carbon-12, and oxygen-16. However, due to the appeal of the classical shell designs single-particle description, this theoretical hypothesis stayed unproven.
Novel Experimental Method
Using an unique experimental approach including the inverted kinematics knockout response, scientists from IMP and their partners have validated the existence of a molecular-type structure in the ground state of beryllium-10, a neutron-rich nucleus.
The experiment was carried out at the Radioactive Isotope Beam Factory (RIBF) at the RIKEN Nishina Center in Japan. In the experiment, a secondary beam of beryllium-10, traveling at half the speed of light, bombarded a 2-millimeter-thick solid hydrogen target. The α-clusters bound within beryllium-10 nuclei were knocked out by protons– with almost no momentum transferred to the recurring nucleus– thus preserving info about the cluster structure in the ground state of beryllium-10.
Molecular-like structure of the beryllium-10 nucleus. Credit: LI Pengjie from IMP
Verifying Long-Standing Hypotheses
The speculative outcomes demonstrated an exceptional agreement in between the speculative cross-sections of knockout responses and theoretical forecasts under tiny designs. This verification supports the long-standing hypothesis regarding the molecular-state structure of beryllium-10s ground state, recommending the formation of an α– α dumbbell-shaped core with two valence neutrons rotating perpendicular to the core axis.
Implications and Future Research
” Similar structures can be discovered on the atomic scale, but they are extremely unusual in the ground state of atomic nuclei,” said Dr. LI Pengjie from IMP, first author of the paper.
This study supplies the first speculative proof for the theoretical description of molecular-state structures in the ground state of atomic nuclei and leads the way for more expedition of the advancement of α-cluster structures in neutron-rich nuclear ground states.
Reference: “Validation of the 10Be Ground-State Molecular Structure Using 10Be( p, pα) 6He Triple Differential Reaction Cross-Section Measurements” by P. J. Li et al., 21 November 2023, Physical Review Letters.DOI: 10.1103/ PhysRevLett.131.212501.
The study was performed in partnership with scientists from the University of Hong Kong, Paris-Saclay University in France, RIKEN and Osaka University in Japan, Nanjing University of Aeronautics and Astronautics, and 22 other research study institutions worldwide.