Researchers from the Institute of Modern Physics at the Chinese Academy of Sciences, led by J. L. Wang, have published a study in the journal Physical Review C that sheds light on the exotic behavior of proton-rich nuclei beyond the proton drip line. The team employed the Gamow shell model (GSM) to investigate the structure and decay of the nucleus silicon-20 (20Si), a candidate for six-proton (6p) emission.
The proton drip line is a boundary in the nuclear landscape beyond which nuclei are so proton-rich that they are unbound and emit protons. Understanding the behavior of these exotic nuclei can provide insights into fundamental nuclear physics and has implications for the energy sector, particularly in the context of nuclear energy and astrophysical processes that power stars and influence the synthesis of elements.
The researchers predict that the ground state of 20Si decays via 6p emission to the ground state of oxygen-14 (14O), with a decay energy of 10.125 MeV and a width of 371 keV. This finding is significant because it provides a theoretical description of the decay process of 20Si, which can guide future experiments aimed at producing and studying this exotic nucleus.
The study also predicts the existence of a 2+ state at 1.7 MeV in 20Si, comparable to that in magnesium-18 (18Mg). This suggests the disappearance of the magic number Z=14 in 20Si, indicating that the traditional shell model may not fully explain the behavior of proton-rich nuclei. Instead, the researchers propose the presence of dynamic Thomas-Ehrman shift (TES) in low-lying states of 20Si and its mirror nuclei, aluminum-19 (19Al) and carbon-20 (20C). The dynamic TES is a phenomenon where the energy levels of a nucleus shift due to the coupling between bound and continuum states.
The practical applications of this research for the energy sector are primarily in the realm of fundamental nuclear physics and astrophysics. Understanding the behavior of exotic nuclei can help improve models of nuclear reactions, which are crucial for developing advanced nuclear energy technologies and understanding the processes that occur in stars and supernovae. Additionally, the study offers the first theoretical description of 20Si, providing a foundation for future experimental and theoretical work in this area.
Source: Physical Review C, Volume 105, Issue 3, March 2022.
This article is based on research available at arXiv.