Explore exotic nuclear landscapes and their impact on the universe

Researchers at Peking University in China have successfully observed the elusive zero.₂⁺ state of ⁸He uncovered a new cluster structure containing two strongly correlated neutron pairs. The discovery provides insight into the exotic nuclear structure and its potential implications for understanding neutron stars. The survey results are physical review letter.

The traditional nuclear model in physics assumes a single-particle picture in which nucleons, protons, and neutrons move independently within the nucleus, forming a well-defined shell structure. Governed by the average potential generated by the nuclear force, nucleons fill different energy levels or shells, leading to increased stability associated with the magic number.

This model, rooted in quantum mechanics, does a good job of explaining the structure and stability of nuclei, but it faces limitations when dealing with exotic nuclei, especially those that are neutron-rich and unstable.

Professor Yan Zhaihong, lead author of the study, explained the team’s motivation to Phys.org: “As nuclear physicists, one of our main goals is to understand what the structure of the nucleus is. It is about understanding what something is and how atomic nuclei arise from complex nuclear interactions between their constituent nucleons. ”

Of particular interest are condensate-like cluster structures within neutron-rich nuclei. ⁸he.

“In neutron-rich nuclei, condensate-like cluster states consisting of one alpha and two di neutron clusters are theoretically predicted. ⁸However, due to the difficulties in both generating and identifying this exotic cluster state, its experimental observation remains elusive,” Professor Yang said.

Cluster state and resonance state ⁸he

The mentioned cluster state refers to a particular nuclear arrangement within a neutron-rich nucleus. ⁸he.

In this state, two strongly correlated neutron pairs, known as di-neutron clusters, combine with an alpha cluster (four helium nuclei) to form what researchers describe as a “condensate-like cluster structure.” Masu.

The term “condensate-like” is analogous to Bose-Einstein condensate (BEC), a state of matter that forms at extremely low temperatures.

In BEC, particles such as atoms occupy the same quantum state and exhibit collective behavior. Similarly, in the following context: ⁸cluster state, this term suggests that the two dineutron clusters and the alpha cluster collectively contribute to the nuclear structure.

Di-neutron clusters are represented as 0.₂⁺“0” indicates spin parity (spin 0 in this case), “2” indicates energy state, and “+” indicates parity (positive).

To observe the theoretical situation, the research team conducted nuclear scattering experiments at the RIKEN Nishina Center in Japan. This experimental effort was designed to explore and scrutinize the internal theoretical cluster conditions. ⁸he.

The focus was on distinctive properties such as the elusive spin parity of the cluster state, the unusually pronounced isoscalar monopole transition strength, and the emission of strongly correlated neutron pairs.

“Together with state-of-the-art theoretical calculations, our results provide strong evidence for the presence of four valence neutrons in the zero-nucleus.₂⁺ state of excitement ⁸“He can form two strongly correlated neutron pairs (di-neutron clusters) and even form exotic condensate-like cluster structures,” said Yanlin Ye, second author of the study. The professor explained.

This achievement not only validates theoretical predictions, but also highlights the ingenuity needed in experimental design to navigate the complexities of nuclear physics.

Speaking of which, Professor Yang said, “One of the direct implications of our discovery is that unstable atomic nuclei at the limit of stability have exotic structures that differ from the conventional single particle or shell model images.” “There is a possibility that this phenomenon could be shown, and it is necessary to improve the atomic nucleus.” Structural theory. ”

“Furthermore, the nucleus is essentially made up of fermion nucleons (protons and neutrons), and our results suggest that the structure of this nucleus is₂⁺ Nevertheless, this state is a bosonic state (a cluster state similar to BEC), consisting of two di-neutron clusters and one alpha cluster. ”

Neutron stars and pulsars

observed 0₂⁺ state of ⁸His influence extends beyond nuclear and quantum physics. This has profound implications for the understanding of astrophysical phenomena, especially the cooling process of neutron stars and glitches in pulsars.

Dr. Yang unraveled the potential connection between 0 and 0.₂⁺ State stars and neutron stars. The observed condensate-like cluster structure is consistent with the suggested beginnings of neutron superfluidity inside a neutron star. This phenomenon is similar to the condensation of electron Cooper pairs in superconductors.

“Although we cannot visit a real neutron star and obtain its dense neutron material, we can infer its properties in the laboratory from experiments with a finite number of atomic nuclei.”

“0₂⁺ This state, characterized by a unique cluster configuration, provides valuable insight into the formation of condensed states of neutron pairs. Importantly, it could be a precursor state for macroscopic condensation of neutron pairs in neutron-rich systems, including neutron stars,” he explained.

This link between nuclear physics and astrophysics not only increases our understanding of exotic nuclear structures, but also provides insight into the complex interactions between the microscopic world of atomic nuclei and the macroscopic realm of neutron stars and pulsars. It also sheds light and contributes to elucidating the mysteries of cosmic phenomena.

The researchers hope to extend their measurements to other neutron-rich nuclei around the neutron drip line (the limit of existence on the nuclear diagram) as they chart a path forward.

“We are particularly interested in how condensate-like cluster structures evolve with more di-neutron clusters. It becomes even more interesting to explore.”

“Generating and identifying such conditions is difficult, but the construction of world-class radioactive ion beam facilities and new detector systems provides a good opportunity,” Professor Ye concluded.