Muons can do something similar, and it has the effect of reducing the effective radius of the atom, which can catalyze fusion.
Which makes me wonder… is antiproton catalyzed fusion a thing? Does the antiproton last long enough? Muons are inefficient to produce. Can antiprotons be made significantly more efficiently?
It is much more difficult to produce antiprotons than muons.
Furthermore, my guess is that the proton-antiproton annihilation rate is much faster than the rate of antiproton-catalyzed fusion. Muon catalysis doesn't have the annihilation channel (the heavy negatively-charged particle is always close to one H/D/T nucleus), so it will catalyze fusions all day until it decays. The antiproton can simply annihilate.
That said, antiprotons probably would catalyze fusion at some rate. Whether it is higher or lower than muon catalysis, I'm not sure. If the antiproton orbital radius is too small, it may actually lower the capture cross-section for a neighboring hydrogen, even if the post-capture fusion cross-section is (almost certainly) higher.
A muon kind of makes sense. It has the same spin and charge as an electron. Kind of mind blowing to think a particle that isn't even a lepton kind of works. I only have a hazy recollection of some engineering level physics but I wouldn't have guessed that.
Which makes me wonder… is antiproton catalyzed fusion a thing? Does the antiproton last long enough? Muons are inefficient to produce. Can antiprotons be made significantly more efficiently?