Breakthrough in nuclear research: Muonic helium-3 reveals secrets!

Breakthrough in nuclear research: Muonic helium-3 reveals secrets!

A research team led by Prof. Dr. Randolf Pohl from Johannes Gutenberg University Mainz has achieved a significant breakthrough in measuring the fundamental properties of atomic nuclei. In experiments conducted at the Paul Scherrer Institute in Switzerland, scientists managed to measure the charge radius of muonic helium-3 with unprecedented precision. The results of this study were published on May 23, 2025 in the renowned journal Science uni-mainz.de reports.

Myoic helium-3, which consists of two protons and a neutron, is significantly different from regular helium because the electron is replaced by a muon. This muon is about 200 times heavier than an electron and allows more precise measurements of the nuclear structure because its large mass increases the overlap of the wave function with the nucleus. The newly determined value for the charge radius of muonic helium-3 is 1.97007 ± 0.00097 femtometers, making it fifteen times more accurate than previous measurements, informed arxiv.org.

Precise measurements and their meaning

Research to determine the charge radius is of central importance because precise values ​​for atomic nuclei are essential for determining fundamental constants of nature and the search for new physical phenomena. The results show good agreement between the muonic helium-3 measurements and previous results obtained on normal helium in Amsterdam. The differences between the charge radii of helium-3 and helium-4 were also precisely determined, indicating the high accuracy of the methodology.

The team, including scientists Prof. Dr. Sonia Bacca, Prof. Dr. Marc Vanderhaeghen and Dr. Franziska Hagelstein, has demonstrated close collaboration in the PRISMA+ Cluster of Excellence by combining theoretical calculations and experimental data. Future plans include examining atomic nuclei from lithium to neon using new types of X-ray detectors to achieve even more precise results.

Comparison to other research results

The new measurement of the charge radius of helium-3 comes in the context of active research into the structure of atomic nuclei. Laser spectroscopy in particular has proven to be a valuable tool, not only for hydrogen, but also for deuterium and other helium isotopes. This also applies to the measurements of muonic deuterium and muonic helium-4, the data from which are currently being analyzed, such as mpg.de reports.

The precision of the new charge radius for helium-3 also has an important role in the benchmark scoring, which is important for theories with few nucleons. In particular, combining these measurements with previous work on the structure of helium-4 and other light nuclei will be crucial to further refine physical models.