Data:CODATA Recommended Values of the Fundamental Physical Constants 1973

Quantity	Symbol	Value	ur
Permeability of vacuum (magnetic constant)	μ0	4π × 10−7 H m−1 ≈ 1.256637061… × 10−6 H m−1	exact
Speed of light in vacuum	c0	2.997 924 58(1.2) × 108 m s−1	4 × 10−9
Permittivity of vacuum (electric constant)	ε0 = (μ0c20)−1	8.854 187 82(7) × 10−12 F m−1	8 × 10−9
Planck constant	h ħ = h/2π	6.626 176 × 10−34 J s 1.054 5887(57) × 10−34 J s	5.4 × 10−6 5.4 × 10−6
Fine structure constant	α = μ0c0e2/2h α−1	0.007 297 3506(60) 137.036 04(11)	8.2 × 10−7 8.2 × 10−7
Gravitational constant	G
Rydberg constant	R∞
Elementary charge	e	1.602 1892(46) × 10−19	2.9 × 10−6
Avogadro constant	NA
Atomic mass unit (atomic mass constant)	1 u = (10−3 kg mol−1)/NA mu
Faraday constant	F = NAe
Molar gas constant	R
Boltzmann constant	k = R/NA
Molar volume, ideal gas (T0 = 273.15 K, p0 = 1 atm)	Vm = RT0/p0
Stefan–Bolzmann constant	σ = (π2/60)k4/ħ3c20
First radiation constant	c1 = 2πhc20
Second radiation constant	c2 = hc0/k
Electron rest mass	me
Muon rest mass	mμ
Proton rest mass	mp
Neutron rest mass	mn
Ratio, proton mass to electron mass	mp/me
Ratio, muon mass to electron mass	mμ/me
Bohr magneton	μB
Nuclear magneton	μN
Electron magnetic moment	μe
Electron g-factor	½ge = μe/μB
Muon magnetic moment	μμ
Muon g-factor	½gμ
Proton magnetic moment	μp
Proton magnetic moment in Bohr magnetons	μp/μB
Proton moment in nuclear magnetons	μp/μN
Ratio, electron to proton magnetic moments	μe/μp
Ratio, muon moment to proton moment	μμ/μp
Proton gyromagnetic ratio	γp
Diamagnetic shielding factor, spherical H2O sample	1 + σ(H2O)
Proton gyromagnetic ratio (uncorrected)	γp γp/2π
Proton moment in nuclear magnetons (uncorrected)	μp/μN
Bohr radius	a0 = α/4πR∞
Josephson frequency–voltage ratio (Josephson constant)	e/2h KJ
Magnetic flux quantum	Φ0 = h/2e h/e
Quantum of circulation	h/2me h/me
Electron Compton wavelength	λC(e) = α2/2R∞ λC(e) = λC(e)/2π = αa0
Proton Compton wavelength	λC(p) = h/mpc0 λC(p) = λC(p)/2π
Neutron Compton wavelength	λC(n) = h/mnc0 λC(n) = λC(n)/2π
Specific electron charge	e/me

Reference

Cohen, E. Richard; Taylor, B. N. The 1973 Least‐Squares Adjustment of the Fundamental Constants. J. Phys. Chem. Ref. Data 1973, 2 (4), 663–734. DOI: 10.1063/1.3253130.