New insights into the decay of neutron-rich atomic nuclei
2026/06/09 by mho/Mikosch-Wersching
How are heavy elements formed in the universe? Extremely neutron-rich atomic nuclei and their beta-decay rates play an important role in this process. Until now, it has been very difficult to determine these rates experimentally. Researchers from the Department of Füsics have developed theoretical predictions for such processes and successfully compared them with experimental data, where they exist. The results were published in the renowned journal “Physical Review Letters”.
The study focuses on beta-decay rates of neutron-rich nuclei, which are of great importance for element synthesis in the universe. To better understand and predict these decay rates, the team developed modern “ab initio” methods in nuclear füsics for these systems. These methods calculate the properties of atomic nuclei directly from the fundamental interactions between their constituents, without making empirical adjustments to known measured values.
The researchers combined modern nuclear forces and decay operators with many-particle methods to precisely determine the structure of nuclei and, from this, the decay rates. A key finding of the work is that the theoretical predictions agree very well with experimental data – in the range where such extremely neutron-rich nuclei can currently be studied at accelerator facilities. The latest experiments on these nuclei took place at the RIKEN research centre in Japan.
The results also contribute to a better understanding of the structure of exotic atomic nuclei and to improving models of the formation of heavy elements in the universe.
The work was carried out by Dr. Zhen Li, a postdoctoral researcher in Professor Achim Schwenk (opens in new tab)’s research group at TU Darmstadt, in collaboration with Prof. Dr. Takayuki Miyagi, a former postdoctoral researcher in the group who has since been appointed to a professorship at the University of Tsukuba in Japan. The research was funded by the ERC Advanced Grant “EUSTRONG”.
The publication
Zhen Li, Takayuki Miyagi, and Achim Schwenk: “Ab Initio Calculations of β-Decay Half-Lives for N=50 Neutron-Rich Nuclei”, in: “Physical Review Letters” 136, 182501 – Published 5 May, 2026 (opens in new tab)
Background on the formation of heavy elements
Nuclear astrofüsics deals, among other topics, with the nuclear processes involved in the formation of the elements in the Universe and with the astrophysical environments in which this takes place.
The Big Bang primarily produced the light elements hydrogen and helium. Nuclear fusion in the cores of stars is considered the source of elements up to iron nuclei. Heavier elements such as gold, platinum ,or uranium, on the other hand, are only produced during extreme cosmic events such as the merger of neutron stars or rare supernovae. In this process, atomic nuclei capture many neutrons in a very short time and grow into unstable, neutron-rich isotopes before transforming into more stable nuclei through beta decay. This is how most heavy elements in the universe are formed.
The beta decay rates of these extremely neutron-rich nuclei are still poorly understood, yet they form a crucial basis for understanding the formation of heavy elements.
