pfp belongs to rsl ( @randomscratcher_lol)

"Muonium is an exotic atom made up of an antimuon and an electron, which was discovered in 1960 by Vernon W. Hughes and is given the chemical symbol Mu.

Its Bohr radius and ionization energy are within 0.5% of hydrogen, deuterium, and tritium, and thus it can usefully be considered as an exotic light isotope of hydrogen." — Wikipedia

kinda no longer use scratch, but find me at @sslonk, my main