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	m_e	= 9.109·10^-31 kg = 5.486·10^-4 u = 0.511 MeV/c²
Proton Mass	m_p	= 1.6726·10^-27 kg = 1.007276 u = 938.27 MeV/c²
Neutron Mass	m_n	= 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	N_A	= 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^-16eV·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 / m_ee²p	= 0.5292·10^-10 m = 0.5292 A°
Compton wavelength, l_c	= h / m_ce	= 2.426·10^-12 m
Fine structure const., a	= e²/ 2 e₀ h c	= 7.29735·10^-3 ~ 1/137
Classical electron radius	= a²a₀	= 2.818·10^-15 m = 2.818 fm
Rydberg constant, R	= a²m_ec / 2 h	= 1.0973·10⁷ m^-1
Hartree energy, E_h	= 2 R h c	= 4.360·10^-18 J = 27.21 eV
Bohr energy, E_b	= R h c	= 2.180·10^-18 J = 13.61 eV