University of Queensland scientists have cracked a long-standing puzzle in nuclear physics, showing that nuclear polarization, once thought to hinder experiments with muonic atoms, has a much smaller effect than expected.
This surprising result clears a major obstacle and paves the way for a new era of atomic research, offering deeper insights into the mysterious inner workings of atomic nuclei using exotic, muon-based atoms.
Breakthrough in Muonic Atom Research
Researchers at the University of Queensland have made a significant breakthrough in muonic atom research, paving the way for new experiments in nuclear physics.
A team from UQ’s School of Mathematics and Physics combined theoretical models and experimental data to demonstrate that nuclear polarization does not significantly interfere with the study of muonic atoms.
Co-author Dr Odile Smits said this discovery removes a key obstacle, allowing scientists to use muonic atoms to gain clearer insights into the magnetic structure of atomic nuclei.
What Are Muonic Atoms?
“Muonic atoms are really fascinating!” Dr. Smits said.
“A muon is a heavy version of the electron and can be produced by cosmic rays or in the lab.
“They can orbit the nucleus just like electrons, forming muonic atoms, but because they are much closer to the nucleus, they see its structure in far greater detail.”
Tidal Effects Inside the Atom
Experiments using muonic atoms have been hindered by uncertainty over how nuclear polarization affects hyperfine structure, which is a small energy splitting within atoms.
Nuclear polarization distorts the shape of the nucleus, in a similar way to how the moon creates tides on Earth.
“Our work has shown that the nuclear polarization effect of muons is far smaller than previously considered,” Dr. Smits said.
The team was led by UQ’s Associate Professor Jacinda Ginges who said the breakthrough removed a major barrier to studying muonic atoms.
“This opens the way for new experiments that will deepen our understanding of nuclear structure and fundamental physics.”
New Pathways for Nuclear Physics
The team worked with Dr. Natalia Oreshkina at the Max Planck Institute for Nuclear Physics in Heidelberg, Germany, who confirmed the results with independent calculations.
The UQ finding will be a stimulus for new experiments with muonic atoms such as at the Paul Scherrer Institute in Zurich where a research program is underway to study these exotic atoms in greater detail.
This research was published in Physical Review Letters.
Reference: “Smallness of the Nuclear Polarization Effect in the Hyperfine Structure of Heavy Muonic Atoms as a Stimulus for Next-Generation Experiments” by J. Vandeleur, G. Sanamyan, O. R. Smits, I. A. Valuev, N. S. Oreshkina and J. S. M. Ginges, 7 March 2025, Physical Review Letters.
DOI: 10.1103/PhysRevLett.134.093003
