Today’s vexing aesthetic physics of handwavium problem:
INASMUCH as the energy levels and resulting orbitals of muon-proton atoms are completely different from those of electron-proton atoms –
WELL, obviously, or what would be the point in making muon metals in the first place –
AND INASMUCH as this makes muon-photon interactions differ remarkably from electron-photon interactions, thus changing radically the emission spectrum and other optical properties from their electronic equivalent –
WHAT do the blasted things look like?
(It is on those mornings when I find myself contemplating this before my first cup of coffee, inasmuch as said metals are a vitally important and visible component of a hypothetical fusion torch drive, that I have some sympathy for the technobabble approach to doing things. Somehow, I doubt the Star Trek writers ever had to deal with this sort of thing…)