I came across muon catalyzed fusion this week. The basic gist of the idea is this: When you replace the electron on a hydrogen atom with a muon, the radius of the atom reduces by a factor of 200. This allows the atom to come much closer to the nuclei of other atoms where there is a finite chance that it will overcome the Gamow barrier penetrating into the other nuclei and achieving nuclear fusion.
The muon is a particle that is identical in every way to the electron except two. It is roughly 200 times more massive than the electron. The extra mass is why it's orbit around the hydrogen nuclei has a radius 1/200th as big as the radius of the electron's orbit. The muon is also short lived. After a few microseconds, it will decay into other particles.
Some of the earliest theoretical work in the field was done by FC Frank at the University of Bristol based on experimental evidence found by Lattes, Occhialini, and Powell both in 1947. None other than J.D. Jackson of "Electrodynamics" fame also worked on the problem of muonized fusion in the 1950's.
I also hadn't realized that experimental work was done on this at my old Alma Matter, the Los Alamos Meson Physics Facility the year before I arrived there.
Picture of the Day