# The Sub-Atomic Constant Page

Keep in mind the following unit conversions:

 1 eV (= electron-volt) = 1.602·10-19 J 1 Å (= Angstrom) = 10-10 m

For further information on all constants you could possibly want to know about, check out NIST. They collect this information as one of their main missions.

 Quantity Symbol Value Atomic mass unit u = 1.6605·10-27 kg = 931.49 MeV/c2 Electron Charge e = 1.602·10-19 C Electron Mass me = 9.109·10-31 kg = 5.486·10-4 u = 0.511 MeV/c2 Proton Mass mp = 1.6726·10-27 kg = 1.007276 u = 938.27 MeV/c2 Neutron Mass mn = 1.6749·10-27 kg = 1.008665 u = 939.57 MeV/c2 Speed of light c = 2.9979·108 m/s Planck's constant h = 6.626·10-34 J·s = 4.136·10-15 eV·s Avogadro's Number NA = 6.0221367·1023 mol-1

Now we can use these constants and form useful combinations with them that make our computations easier:

 Quantity Formula Value (= hbar) = h / (2p) = 1.0546·10-34 J·s = 6.582·10-16 eV·s h·c = 1.9864·10-25 J·m = 1.240·10-6 eV·m ·c = 3.161·10-26 J·m = 1.9734·10-7 eV·m = 197.34 MeV·fm e / h = 2.418·1014 A/J Bohr radius, a0 = e0 h2 / me e2 p = 0.5292·10-10 m = 0.5292 A° Compton wavelength, lc = h / mc e = 2.426·10-12 m Fine structure const., a = e2 / 2 e0 h c = 7.29735·10-3 ~ 1/137 Classical electron radius = a2 a0 = 2.818·10-15 m = 2.818 fm Rydberg constant, R = a2 me c / 2 h = 1.0973·107 m-1 Hartree energy, Eh = 2 R h c = 4.360·10-18 J = 27.21 eV Bohr energy, Eb = R h c = 2.180·10-18 J = 13.61 eV