"Rydberg unit of energy" -- planck constant (exact value since 2019 definition of kilogram) h = 6.62607015 10^(-34) joule second -- electron mass me = 9.1093837015 10^(-31) kilogram -- elementary charge e = 1.602176634 10^(-19) coulomb -- vacuum electric permittivity epsilon0 = 8.8541878128 10^(-12) farad / meter -- derived units joule = kilogram meter^2 / second^2 coulomb = ampere second volt = joule / coulomb farad = coulomb / volt -- base units (for printing) ampere = "ampere" kilogram = "kilogram" meter = "meter" second = "second" -- rydberg unit of energy Ry = me e^4 / (8 h^2 epsilon0^2) -- convert to electron volts Ry = Ry 1/e coulomb / joule "eV" Ry Run