There is a convoluted naming history involving muonium and true muonium. It is too complicated to even tackle in a short posting.
To backtrack - any scenario where protons or deuterons, in close proximity or in an actual fusion event can "make" muons, even if they first make another shorter-lived particle - faces an obstacle. The obstacle is conservation of charge. To cut to the chase, we can surmise the antimuon as one general solution, and another is the positron - but another twist on the inquiry is a particle which does not turn up easily in an online search. That could be because it is impossible - but imagine this . a positron orbiting a muon. What do you call it? I labeled it as a positromuon, but that sounds pretty lame. It is really weird with the positive charge orbiting the heavier negatively charged muon. It would be highly reactive, on paper, but since it probably cannot exist in our 3-space, the most interesting thing about is that its ionization potential is "probably" the same 6.8 eV as positronium, in which case it has Rydberg energy written all over it. Almost as strange as the blood moon eclipse.
