A cold fusion mechanism that actually works — using muons to replace electrons in hydrogen molecules, bringing nuclei close enough to fuse at room temperature, but limited by the muon’s short lifetime.
ReviewedLast reviewed: 9 Aug 2026·Category: Concepts & Physics
How It Works
A muon (μ−) is a heavy cousin of the electron, about 207 times more massive. When a negative muon replaces an electron in a deuterium or tritium molecule, the resulting “muonic molecule” is ~207 times smaller than a normal molecule. The nuclei are so close together that they tunnel through the Coulomb barrier and fuse, even at room temperature.[1]
The sticking problem: After catalysing a D–T fusion reaction, the muon is usually released and goes on to catalyse another reaction (about 150 reactions per muon lifetime). However, approximately 0.5–1% of the time, the muon “sticks” to the helium-4 product and is lost. Since muons are expensive to produce (each requires ~5 GeV of accelerator energy), the sticking fraction makes energy breakeven currently impossible.
History
Muon-catalysed fusion was first predicted by Frank in 1947 and observed by Alvarez in 1957. Jones and colleagues at Los Alamos demonstrated ~150 fusions per muon in D–T mixtures in the 1980s. The concept generated excitement but was ultimately limited by the sticking fraction.[2]
Status
Muon-catalysed fusion remains a subject of scientific interest but is not considered a viable path to energy production with current technology. Reducing the sticking fraction or dramatically reducing the cost of muon production would be required for energy applications.[3]
Sources
Rafelski, J. and Jones, S.E. "Cold nuclear fusion." Scientific American, 257, 84–89, 1987.
Breunlich, W.H. et al. "Muon-catalyzed fusion." Annual Review of Nuclear and Particle Science, 39, 311–355, 1989.
Nagamine, K. Introductory Muon Science. Cambridge University Press, 2003.