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Physics LibreTexts

66.25: Fundamental Physical Constants — Extensive Listing

( \newcommand{\kernel}{\mathrm{null}\,}\)

Table 66.25.1: Universal Fundamental Constants

Quantity Symbol Value Unit Relative std.
uncert. u_{\mathrm{r}}
speed of light in vacuum c

299792458

 m s1 exact
vacuum magnetic permeability 4πα/e2c μ0 1.25663706212(19)×106 NA2 1.5×1010
μ0/(4π×107) 1.00000000055(15) NA2 1.5×1010
vacuum electric permittivity 1/μ0c2 ϵ0 8.8541878128(13)×1012  F m1 1.5×1010
characteristic impedance of vacuum μ0c Z0 376.730313668(57) Ω 1.5×1010
Newtonian constant of gravitation G 6.67430(15)×1011  m3 kg1 s2 2.2×105
  G/c 6.70883(15)×1039 (GeV/c2)2 2.2×105
Planck constant* h 6.62607015×1034  J Hz1 exact
    4.135667696×1015 eVHz1 exact
  1.054571817×1034 Js exact
    6.582119569×1016 eVs exact
  c 197.3269804 MeVfm exact
Planck mass (c/G)1/2 mP 2.176434(24)×108  kg 1.1×105
energy equivalent mPc2 1.220890(14)×1019 GeV 1.1×105
Planck temperature (c5/G)1/2/k TP 1.416784(16)×1032 K 1.1×105
Planck length /mPc=(G/c3)1/2 lP 1.616255(18)×1035  m 1.1×105
Planck time lP/c=(G/c5)1/2 tP 5.391247(60)×1044 s 1.1×105

Table 66.25.2: Electromagnetic Constants

Quantity Symbol Value Unit Relative std.
uncert. u_{\mathrm{r}}
elementary charge e 1.602176634×1019 C exact
         
  e/ 1.519267447×1015  A J1 exact
magnetic flux quantum 2π/(2e) Φ0 2.067833848×1015  Wb exact
conductance quantum 2e2/2π G0 7.748091729×105  S exact
inverse of conductance quantum G10 12906.40372 Ω exact
Josephson constant 2e/h KJ 483597.8484×109  Hz V1 exact
von Klitzing constant μ0c/2α=2π/e2 RK 25812.80745 Ω exact
Bohr magneton e/2me μB 9.2740100783(28)×1024  J T1 3.0×1010
    5.7883818060(17)×105 eVT1 3.0×1010
  μB/h 1.39962449361(42)×1010  Hz T1 3.0×1010
  μB/hc 46.686447783(14) [m1 T1] 3.0×1010
  μB/k 0.67171381563(20) KT1 3.0×1010
nuclear magneton e/2mp μN 5.0507837461(15)×1027  J T1 3.1×1010
    3.15245125844(96)×108 eVT1 3.1×1010
  μN/h 7.6225932291(23) MHzT1 3.1×1010
  μN/hc 2.54262341353(78)×102 [ m1 T1] 3.1×1010
  μN/k 3.6582677756(11)×104  K T1 3.1×1010

Table 66.25.3: General Atomic and Nuclear Constants

Quantity Symbol Value Unit Relative std.
uncert. u_{\mathrm{r}}
fine-structure constant e2/4πϵ0c α 7.2973525693(11)×103 1.5×1010
inverse fine-structure constant α1 137.035999084(21) 1.5×1010
Rydberg frequency α2mec2/2h=Eh/2h cR 3.2898419602508(64)×1015  Hz 1.9×1012
energy equivalent hcR 2.1798723611035(42)×1018  J 1.9×1012
    13.605693122994(26) eV 1.9×1012
Rydberg constant R 10973731.568160(21) [m1] 1.9×1012
Bohr radius /αmec=4πϵ02/mee2 a0 5.29177210903(80)×1011  m 1.5×1010
Hartree energy α2mec2=e2/4πϵ0a0=2hcR Eh 4.3597447222071(85)×1018  J 1.9×1012
    27.211386245988(53) eV 1.9×1012
quantum of circulation π/me 3.6369475516(11)×104  m2 s1 3.0×1010
  2π/me 7.2738951032(22)×104  m2 s1 3.0×1010

Table 66.25.4: Electroweak Constants

Quantity Symbol Value Unit Relative std.
uncert. u_{\mathrm{r}}
Fermi coupling constant GF/(c)3 1.1663787(6)×105 GeV2 5.1×107
sin2θW=s2W1(mW/mZ)2 sin2θW 0.22290(30) 1.3×103
Quantity Symbol Value Unit Relative std.
uncert. u_{\mathrm{r}}
electron mass me 9.1093837015(28)×1031 kg 3.0×1010
    5.48579909065(16)×104 u 2.9×1011
energy equivalent mec2 8.1871057769(25)×1014 J 3.0×1010
    0.51099895000(15) MeV 3.0×1010
electron-muon mass ratio me/mμ 4.83633169(11)×103 2.2×108
electron-tau mass ratio me/mτ 2.87585(19)×104 6.8×105
electron-proton mass ratio me/mp 5.44617021487(33)×104 6.0×1011
electron-neutron mass ratio me/mn 5.4386734424(26)×104 4.8×1010
electron-deuteron mass ratio me/md 2.724437107462(96)×104 3.5×1011
electron-triton mass ratio me/mt 1.819200062251(90)×104 5.0×1011
electron-helion mass ratio me/mh 1.819543074573(79)×104 4.3×1011
electron to alpha particle mass ratio me/mα 1.370933554787(45)×104 3.3×1011
electron charge to mass quotient e/me 1.75882001076(53)×1011 Ckg1 3.0×1010
electron molar mass NAme M(e),Me 5.4857990888(17)×107  kg mol1 3.0×1010
reduced Compton wavelength /mec=αa0 λC 3.8615926796(12)×1013  m 3.0×1010
Compton wavelength λC 2.42631023867(73)×1012 [ m] 3.0×1010
classical electron radius α2a0 re 2.8179403262(13)×1015  m 4.5×1010
Thomson cross section (8π/3)r2e σe 6.6524587321(60)×1029  m2 9.1×1010
electron magnetic moment μe 9.2847647043(28)×1024  J T1 3.0×1010
to Bohr magneton ratio μe/μB 1.00115965218128(18) 1.7×1013
to nuclear magneton ratio μe/μN 1838.28197188(11) 6.0×1011
electron magnetic moment        
anomaly |μe|/μB1 ae 1.15965218128(18)×103 1.5×1010
electron g-factor (2(1+ae)) ge 2.00231930436256(35) 1.7×1013
electron-muon magnetic moment ratio μe/μμ 206.7669883(46) 2.2×108
electron-proton magnetic moment ratio
electron to shielded proton magnetic
μe/μp 658.21068789(20) 3.0×1010
moment ratio (H2O,sphere,25C) μe/μp 658.2275971(72)\) 1.1×108
electron-neutron magnetic moment ratio μe/μn 960.92050(23) 2.4×107
electron-deuteron magnetic moment ratio
electron to shielded helion magnetic
μe/μd 2143.9234915(56) 2.6×109
moment ratio (gas, sphere, 25C ) μe/μh 864.058257(10) 1.2×108
electron gyromagnetic ratio 2|μe|/ γe 1.76085963023(53)×1011  s1 T1 3.0×1010
    28024.9514242(85) MHzT1 3.0×1010

Table 66.25.6: Muon, mu

Quantity Symbol Value Unit Relative std.
uncert. u_{\mathrm{r}}
muon mass mμ 1.883531627(42)×1028  kg 2.2×108
    0.1134289259(25) u 2.2×108
energy equivalent   1.692833804(38)×1011  J 2.2×108
  mμc2 105.6583755(23) MeV 2.2×108
muon-electron mass ratio mμ/me 206.7682830(46)   2.2×108
muon-tau mass ratio mμ/mτ 5.94635(40)×102   6.8×105
muon-proton mass ratio mμ/mp 0.1126095264(25)   2.2×108
muon-neutron mass ratio mμ/mn 0.1124545170(25)   2.2×108
muon molar mass NAmμ M(μ),Mμ 1.134289259(25)×104  kg mol1 2.2×108
reduced muon Compton wavelength /mμc λC,μ 1.867594306(42)×1015  m 2.2×108
muon Compton wavelength λC,μ 1.173444110(26)×1014 [ m] 2.2×108
muon magnetic moment μμ 4.49044830(10)×1026  J T1 2.2×108
to Bohr magneton ratio μμ/μB 4.84197047(11)×103   2.2×108
to nuclear magneton ratio μμ/μN 8.89059703(20)   2.2×108
muon magnetic moment anomaly       5.4×107
|μμ|/(e/2mμ)1 aμ 1.16592089(63)×103 6.3×1010
muon g-factor 2(1+aμ) gμ 2.0023318418(13) 2.2×108
muon-proton magnetic moment ratio μμ/μp 3.183345142(71)  

Table 66.25.7: Tau, tau

Quantity Symbol Value Unit Relative std.
uncert. u_{\mathrm{r}}
tau mass mτ 3.16754(21)×1027  kg 6.8×105
    1.90754(13) u 6.8×105
energy equivalent mτc2 2.84684(19)×1010  J 6.8×105
    1776.86(12) MeV 6.8×105
tau-electron mass ratio mτ/me 3477.23(23)   6.8×105
tau-muon mass ratio mτ/mμ 16.8170(11)   6.8×105
tau-proton mass ratio mτ/mp 1.89376(13)   6.8×105
tau-neutron mass ratio mτ/mn 1.89115(13)   6.8×105
tau molar mass NAmτ MC,τ 1.90754(13)×103  kg mol1 6.8×105
reduced tau Compton wavelength /mτc λC,τ 1.110538(75)×1016 [ m] 6.8×105
tau Compton wavelength λC,τ 6.97771(47)×1016 [m] 6.8×105

Table 66.25.8: Proton, p

Quantity Symbol Value Unit Relative std.
uncert. u_{\mathrm{r}}
proton-tau mass ratio mp/mτ 0.528051(36)   6.8×105
proton-neutron mass ratio mp/mn 0.99862347812(49)   4.9×1010
proton charge to mass quotient e/mp 9.5788331560(29)×107 Ckg1 3.1×1010
proton molar mass NAmp M(p),Mp 1.00727646627(31)×103  kg mol1 3.1×1010
reduced proton Compton wavelength /mpc λC,p 2.10308910336(64)×1016 \( m 3.1×1010
proton Compton wavelength λC,p 1.32140985539(40)×1015 [ m] 3.1×1010
proton rms charge radius rp 8.414(19)×1016  m 2.2×103
proton magnetic moment μp 1.41060679736(60)×1026  J T1 4.2×1010
to Bohr magneton ratio μp/μB 1.52103220230(46)×103   3.0×1010
to nuclear magneton ratio μp/μN 2.79284734463(82)   2.9×1010
proton g-factor 2μp/μN gp 5.5856946893(16)   2.9×1010
proton-neutron magnetic moment ratio μp/μn 1.45989805(34)   2.4×107
shielded proton magnetic moment
μp 1.410570560(15)×1026  J T1 1.1×108
(H2O, sphere, 25C)        
to Bohr magneton ratio μp/μB 1.520993128(17)×103   1.1×108
to nuclear magneton ratio μp/μN 2.792775599(30)   1.1×108
proton magnetic shielding correction        
1μp/μp(H2O,sphere,25C) σp 2.5689(11)×105   4.2×104
proton gyromagnetic ratio 2 μp/ γp 2.6752218744(11) \times 10^8 \mathrm{~s}^{-1} \mathrm{~T}^{-1} 4.2 \times 10^{-10}
    42.577 478 518(18) \mathrm{MHz} \mathrm{T}^{-1} 4.2 \times 10^{-10}
shielded proton gyromagnetic ratio        
2 \mu_{\mathrm{p}}^{\prime} / \hbar\left(\mathrm{H}_2 \mathrm{O}\right., sphere, \left.25^{\circ} \mathrm{C}\right) \gamma_{\mathrm{p}}^{\prime} 2.675153151(29) \times 10^8 \mathrm{~s}^{-1} \mathrm{~T}^{-1} 1.1 \times 10^{-8}
    42.57638474(46) \mathrm{MHz} \mathrm{T}^{-1} 1.1 \times 10^{-8}

Table \PageIndex{9}: Neutron, n

Quantity Symbol Value Unit Relative std.
uncert. u_{\mathrm{r}}
neutron mass m_{\mathrm{n}} 1.67492749804(95) \times 10^{-27}
\mathrm{kg}
5.7 \times 10^{-10}
    1.008 664 915 95(49) \mathrm{u} 4.8 \times 10^{-10}
\quad energy equivalent m_{\mathrm{n}} c^2 1.50534976287(86) \times 10^{-10}
\mathrm{J} 5.7 \times 10^{-10}
    939.565 420 52(54) \mathrm{MeV} 5.7 \times 10^{-10}
neutron-electron mass ratio m_{\mathrm{n}} / m_{\mathrm{e}} 1838.68366173(89)   4.8 \times 10^{-10}
neutron-muon mass ratio m_{\mathrm{n}} / m_\mu 8.89248406(20)   2.2 \times 10^{-8}
neutron-tau mass ratio m_{\mathrm{n}} / m_\tau 0.528779(36)   6.8 \times 10^{-5}
neutron-proton mass ratio m_{\mathrm{n}} / m_{\mathrm{p}} 1.00137841931(49)   4.9 \times 10^{-10}
neutron-proton mass difference m_{\mathrm{n}}-m_{\mathrm{p}} 2.30557435(82) \times 10^{-30 } \mathrm{kg}
3.5 \times 10^{-7}
    1.38844933(49) \times 10^{-3} \mathrm{u} 3.5 \times 10^{-7}
\quad energy equivalent \left(m_{\mathrm{n}}-m_{\mathrm{p}}\right) c^2 2.07214689(74) \times 10^{-13}
\mathrm{J}
3.5 \times 10^{-7}
    1.29333236(46) \mathrm{MeV} 3.5 \times 10^{-7}
neutron molar mass N_{\mathrm{A}} m_{\mathrm{n}} M(\mathrm{n}), M_{\mathrm{n}} 1.00866491560(57) \times 10^{-3} \mathrm{~kg} \mathrm{~mol}^{-1} 5.7 \times 10^{-10}
reduced neutron Compton wavelength \hbar / m_{\mathrm{n}} c
\( \lambda_{\mathrm{C}, \mathrm{n}\) 2.1001941552(12) \times 10^{-16}
\mathrm{m } 5.7 \times 10^{-10}
neutron Compton wavelength \( \lambda_{\mathrm{C}, \mathrm{n}\) 1.31959090581(75) \times 10^{-15} [\mathrm{m}]^{\dagger} 5.7 \times 10^{-10}
neutron magnetic moment

\mu_{\mathrm{n}}

-9.6623651(23) \times 10^{-27} \mathrm{~J} \mathrm{~T}^{-1} 2.4 \times 10^{-7}
\quad to Bohr magneton ratio \mu_{\mathrm{n}} / \mu_{\mathrm{B}} -1.04187563(25) \times 10^{-3}   2.4 \times 10^{-7}
\quad to nuclear magneton ratio \mu_{\mathrm{n}} / \mu_{\mathrm{N}} -1.91304273(45)   2.4 \times 10^{-7}
neutron g-factor 2 \mu_{\mathrm{n}} / \mu_{\mathrm{N}} g_{\mathrm{n}} -3.82608545(90)   2.4 \times 10^{-7}
neutron-electron magnetic moment ratio \mu_{\mathrm{n}} / \mu_{\mathrm{e}} 1.04066882(25) \times 10^{-3}   2.4 \times 10^{-7}
neutron-proton magnetic moment ratio \mu_{\mathrm{n}} / \mu_{\mathrm{p}} -0.68497934(16)   2.4 \times 10^{-7}
neutron to shielded proton magnetic        
\quad moment ratio \left(\mathrm{H}_2 \mathrm{O}\right., sphere, \left.25^{\circ} \mathrm{C}\right) \mu_{\mathrm{n}} / \mu_{\mathrm{p}}^{\prime} -0.68499694(16)   2.4 \times 10^{-7}
neutron gyromagnetic ratio 2\left|\mu_{\mathrm{n}}\right| / \hbar \gamma_{\mathrm{n}} 1.83247171(43) \times 10^8 \mathrm{~s}^{-1} \mathrm{~T}^{-1} 2.4 \times 10^{-7}
    29.1646931(69) \mathrm{MHz} \mathrm{T}^{-1} 2.4 \times 10^{-7}

Table \PageIndex{10}: Deuteron, d

Quantity Symbol Value Unit Relative std.
uncert. u_{\mathrm{r}}
deuteron mass m_{\mathrm{d}} 3.3435837768(10) \times 10^{-27} kg 3.1 \times 10^{-10}
    2.013553212544(15) u 7.4 \times 10^{-12}
iivalent m_{\mathrm{d}} c^2 3.00506323491(94) \times 10^{-10} J 3.1 \times 10^{-10}
deuteron-electron mass ratio m_{\mathrm{d}} / m_{\mathrm{e}} 3670.4829676555(63) MeV 3.1 \times 10^{-10}
deuteron-proton mass ratio m_{\mathrm{d}} / m_{\mathrm{p}} 1.9990075012699(84)   1.7 \times 10^{-11}
deuteron molar mass N_{\mathrm{A}} m_{\mathrm{d}} M(\mathrm{~d}), M_{\mathrm{d}} 2.01355321466(63) \times 10^{-3}   4.2 \times 10^{-12}
deuteron rms charge radius r_{\mathrm{d}} 2.12778(27) \times 10^{-15} \( \mathrm{~kg} \mathrm{~mol}^{-1} 3.1 \times 10^{-10}
deuteron magnetic moment \mu_{\mathrm{d}} 4.330735087(11) \times 10^{-27} \mathrm{~m}^{-1} 1.3 \times 10^{-4}
to Bohr magneton ratio \mu_{\mathrm{d}} / \mu_{\mathrm{B}} 4.669754568(12) \times 10^{-4}   2.6 \times 10^{-9}
to nuclear magneton ratio \mu_{\mathrm{d}} / \mu_{\mathrm{N}} 0.8574382335(22)   2.6 \times 10^{-9}
deuteron g-factor \mu_{\mathrm{d}} / \mu_{\mathrm{N}} g_{\mathrm{d}} 0.8574382335(22)   2.6 \times 10^{-9}
deuteron-electron magnetic moment ratio \mu_{\mathrm{d}} / \mu_{\mathrm{e}} -4.664345550(12) \times 10^{-4}   2.6 \times 10^{-9}
deuteron-proton magnetic moment ratio \mu_{\mathrm{d}} / \mu_{\mathrm{p}} 0.30701220930(79)   2.6 \times 10^{-9}
deuteron-neutron magnetic moment ratio \mu_{\mathrm{d}} / \mu_{\mathrm{n}} -0.44820652(11)   2.6 \times 10^{-9}
         

Table \PageIndex{11}: Triton, t

Quantity Symbol Value Unit Relative std.
uncert. u_{\mathrm{r}}
triton mass m_{\mathrm{t}} 5.0073567512(16) \times 10^{-27} kg 3.1 \times 10^{-10}
    3.01550071597(10) u 3.4 \times 10^{-11}
energy equivalent m_{\mathrm{t}} c^2 4.5003878119(14) \times 10^{-10} J 3.1 \times 10^{-10}
    2808.92113668(88) MeV 3.1 \times 10^{-10}
triton-electron mass ratio m_{\mathrm{t}} / m_{\mathrm{e}} 5496.92153551(21) 3.8 \times 10^{-11}
triton-proton mass ratio m_{\mathrm{t}} / m_{\mathrm{p}}     3.4 \times 10^{-11}
triton molar mass N_{\mathrm{A}} m_{\mathrm{t}} M(\mathrm{t}), M_{\mathrm{t}} 3.01550071913(94) \times 10^{-3} \mathrm{~kg} \mathrm{~mol}^{-1} 3.1 \times 10^{-10}
triton magnetic moment \mu_{\mathrm{t}} 1.5046095178(30) \times 10^{-26} \mathrm{~J} \mathrm{~T}^{-1} 2.0 \times 10^{-9}
to Bohr magneton ratio \mu_{\mathrm{t}} / \mu_{\mathrm{B}} 1.6223936648(32) \times 10^{-3} 2.0 \times 10^{-9}
to nuclear magneton ratio \mu_{\mathrm{t}} / \mu_{\mathrm{N}} 2.9789624650(59)   2.0 \times 10^{-9}
triton g-factor 2 \mu_{\mathrm{t}} / \mu_{\mathrm{N}} g_{\mathrm{t}}     2.0 \times 10^{-9}
         

Table \PageIndex{12}: Helion, h

Quantity Symbol Value Unit Relative std.
uncert. u_{\mathrm{r}}
helion mass m_{\mathrm{h}} 5.0064127862(16) \times 10^{-27} kg 3.1 \times 10^{-10} 25 \times 10^{-11}
    3.014932246932(74)   2.5 \times 10^{-11}
energy equivalent m_{\mathrm{h}} c^2 4.4995394185(14) \times 10^{-10} J 3.1 \times 10^{-10}
    2808.39161112(88) MeV 3.1 \times 10^{-10}
helion-electron mass ratio m_{\mathrm{h}} / m_{\mathrm{e}} 5495.88527984(16)   2.9 \times 10^{-11}
helion-proton mass ratio m_{\mathrm{h}} / m_{\mathrm{p}} 2.993152671552(70)   2.4 \times 10^{-11}
helion molar mass N_{\mathrm{A}} m_{\mathrm{h}} M(\mathrm{~h}), M_{\mathrm{h}} 3.01493225010(94) \times 10^{-3} \mathrm{~kg} \mathrm{~mol}^{-1} 3.1 \times 10^{-10}
helion magnetic moment \mu_{\mathrm{h}} -1.07461755198(93) \times 10^{-26} \mathrm{~J} \mathrm{~T}^{-1} 8.7 \times 10^{-10}
to Bohr magneton ratio \mu_{\mathrm{h}} / \mu_{\mathrm{B}} -1.15874098083(94) \times 10^{-3}   8.1 \times 10^{-10}
to nuclear magneton ratio \mu_{\mathrm{h}} / \mu_{\mathrm{N}} -2.1276253498(17)   8.1 \times 10^{-10}
helion g-factor 2 \mu_{\mathrm{h}} / \mu_{\mathrm{N}} g_{\mathrm{h}} -4.2552506995(34)   8.1 \times 10^{-10}
shielded helion magnetic moment
(gas, sphere, 25^{\circ} \mathrm{C} )
\mu_{\mathrm{h}}^{\prime} -1.07455311035(93) \times 10^{-26} \( \mathrm{~J} \mathrm{~T}^{-1} 8.7 \times 10^{-10}
to Bohr magneton ratio \mu_{\mathrm{h}}^{\prime} / \mu_{\mathrm{B}} -1.15867149457(94) \times 10^{-3}   8.1 \times 10^{-10}
to nuclear magneton ratio \mu_{\mathrm{h}}^{\prime} / \mu_{\mathrm{N}} -2.1274977624(17)   8.1 \times 10^{-10}
shielded helion to proton magnetic
moment ratio (gas, sphere, 25^{\circ} \mathrm{C} )
shielded helion to shielded proton magnetic
\mu_{\mathrm{h}}^{\prime} / \mu_{\mathrm{p}} -0.76176657721(66)   8.6 \times 10^{-10}
moment ratio (gas / \mathrm{H}_2 \mathrm{O}, spheres, 25^{\circ} \mathrm{C} ) \mu_{\mathrm{h}}^{\prime} / \mu_{\mathrm{p}}^{\prime} -0.761 7861334(31)   4.0 \times 10^{-9}
shielded helion gyromagnetic ratio        
2\left|\mu_{\mathrm{h}}^{\prime}\right| / \hbar \text { (gas, sphere, } 25^{\circ} \mathrm{C} \text { ) } \gamma_{\mathrm{h}}^{\prime} 2.0378946078(18) \times 10^8 \mathrm{s}^{-1} \mathrm{~T}^{-1} 8.7 \times 10^{-10}
    32.434100033(28) \mathrm{MHz} \mathrm{T}^{-1} 8.7 \times 10^{-10}

Table \PageIndex{13}: Alpha particle, \alpha

Quantity Symbol Value Unit Relative std.
uncert. u_{\mathrm{r}}
alpha particle mass m_\alpha 6.6446573450(21) \times 10^{-27} kg 3.1 \times 10^{-10}
energy equivalent   4.001506179129(62) u 1.6 \times 10^{-11}
  m_\alpha c^2 5.9719201997(19) \times 10^{-10} J 3.1 \times 10^{-10}
alpha particle to electron mass ratio   3727.3794118(12) MeV 3.1 \times 10^{-10}
alpha particle to proton mass ratio m_\alpha / m_{\mathrm{e}} 7294.29954171(17)   2.4 \times 10^{-11}
alpha particle rms charge radius m_\alpha / m_{\mathrm{p}} 3.972599690252(70)\)   1.8 \times 10^{-11}
alpha particle molar mass N_{\mathrm{A}} m_\alpha r_\alpha 1.6785(21) \times 10^{-15} m 1.2 \times 10^{-3}
  M(\alpha), M_\alpha 4.0015061833(12) \times 10^{-3} \(\mathrm{~kg} \mathrm{~mol}^{-1} 3.1 \times 10^{-10}
         

Table \PageIndex{14}: Physicochemical Constants

Quantity Symbol Value Unit Relative std.
uncert. u_{\mathrm{r}}
Avogadro constant
N_{\mathrm{A}} 6.02214076 \times 10^{23} \mathrm{~mol}^{-1} exact
Boltzmann constant k 1.380649 \times 10^{-23} \mathrm{~J} \mathrm{~K}^{-1} exact
    8.617333262 \ldots \times 10^{-5} \mathrm{eV} \mathrm{K}^{-1} exact
  k / h 2.083661912 \ldots \times 10^{10} \mathrm{~Hz} \mathrm{~K}^{-1} exact
  k / h c 69.50348004 \ldots \left[\mathrm{m}^{-1} \mathrm{~K}^{-1}\right]^{\dagger} exact
atomic mass constant        
m_{\mathrm{u}}=\frac{1}{12} m\left({ }^{12} \mathrm{C}\right)=2 h c R_{\infty} / \alpha^2 c^2 A_{\mathrm{r}}(\mathrm{e}) m_{\mathrm{u}} 1.66053906892(52) \times 10^{-27}\) kg 3.1 \times 10^{-10}
equivalent energy m_{\mathrm{u}} c^2 \) 1.49241808768(46) \times 10^{-10} J 3.1 \times 10^{-10}
    931.49410372(29) MeV 3.1 \times 10^{-10}
molar mass constant { }^{\|} M_{\mathrm{u}} 1.00000000105(31) \times 10^{-3} \mathrm{~kg} \mathrm{~mol}^{-1} 3.1 \times 10^{-10}
molar mass" of carbon-12 A_{\mathrm{r}}\left({ }^{12} \mathrm{C}\right) M_{\mathrm{u}} M\left({ }^{12} \mathrm{C}\right) 12.0000000126(37) \times 10^{-3} \mathrm{~kg} \mathrm{~mol}^{-1} 3.1 \times 10^{-10}
molar Planck constant N_{\mathrm{A}} h 3.990312712 \ldots \times 10^{-10} \mathrm{~J} \mathrm{~Hz}^{-1} \mathrm{~mol}^{-1} exact
molar gas constant N_{\mathrm{A}} k R 8.314462618 \ldots \mathrm{J} \mathrm{mol}^{-1} \mathrm{~K}^{-1} exact
Faraday constant N_{\mathrm{A}} e F 96485.33212 \ldots \mathrm{C} \mathrm{mol}^{-1} exact
standard-state pressure   100000 Pa exact
standard atmosphere   101325 Pa exact
molar volume of ideal gas R T / p        
T=273.15 \mathrm{~K}, p=100 \mathrm{kPa}
or standard-state pressure
V_{\mathrm{m}} 22.71095464 \ldots \times 10^{-3} \mathrm{~m}^3 \mathrm{~mol}^{-1} exact
Loschmidt constant N_{\mathrm{A}} / V_{\mathrm{m}}
molar volume of ideal gas R T / p
n_0 2.651645804 \ldots \times 10^{25} \mathrm{~m}^{-3} exact
T=273.15 \mathrm{~K}, p=101.325 \mathrm{kPa}
or standard atmosphere
V_{\mathrm{m}} 22.41396954 \ldots \times 10^{-3} \mathrm{~m}^3 \mathrm{~mol}^{-1} exact
Loschmidt constant N_{\mathrm{A}} / V_{\mathrm{m}} n_0 2.686780111 \ldots \times 10^{25} \mathrm{~m}^{-3} exact
Sackur-Tetrode (absolute entropy) constant**        

\frac{5}{2}+\ln \left[\left(m_{\mathrm{u}} k T_1 / 2 \pi \hbar^2\right)^{3 / 2} k T_1 / p_0\right]

T_1=1 \mathrm{~K}, p_0=100 \mathrm{kPa}
or standard-state pressure

S_0 / R -1.15170753496(47)   4.1 \times 10^{-10}
T_1=1 \mathrm{~K}, p_0=101.325 \mathrm{kPa}
or standard atmosphere
  -1.16487052149(47)   4.0 \times 10^{-10}
Stefan-Boltzmann constant
\left(\pi^2 / 60\right) k^4 / \hbar^3 c^2
\sigma 5.670374419 \ldots \times 10^{-8} \mathrm{~W} \mathrm{~m}^{-2} \mathrm{~K}^{-4} exact
first radiation constant for spectral        
radiance 2 h c^2 \mathrm{sr}^{-1} c_{1 \mathrm{~L}} 1.191042972 \ldots \times 10^{-16} \left[\mathrm{~W} \mathrm{~m}^2 \mathrm{sr}^{-1}\right]^{\dagger} exact
first radiation constant 2 \pi h c^2=\pi \mathrm{sr} c_{1 \mathrm{~L}} c_1 3.741771852 \ldots \times 10^{-16} \left[\mathrm{~W} \mathrm{~m}^2\right]^{\dagger} exact
second radiation constant h c / k c_2 1.438776877 \ldots \times 10^{-2} [\mathrm{~m} \mathrm{~K}]^{\dagger} exact
Wien displacement law constants        
b=\lambda_{\max } T=c_2 / 4.965114231 \ldots b 2.897771955 \ldots \times 10^{-3} [\mathrm{~m} \mathrm{~K}]^{\dagger} exact
b^{\prime}=\nu_{\max } / T=2.821439372 \ldots c / c_2 b^{\prime} 5.878925757 \ldots \times 10^{10} Hz K exact
         

* The energy of a photon with frequency \nu expressed in unit Hz is E=h \nu in J . Unitary time evolution of the state of this photon is given by \exp (-i E t / \hbar)|\varphi\rangle, where |\varphi\rangle is the photon state at time t=0 and time is expressed in unit s. The ratio E t / \hbar is a phase.

{ }^{\dagger} The symbol [\mathrm{m}] denotes \mathrm{m} /(\mathrm{Hz} \mathrm{s}). If angles are dimensionless, as in the current SI , then \mathrm{Hz} \mathrm{s}=1. If angles have a dimension, then \mathrm{Hz} \mathrm{s}= cycle.
‡ Value recommended by the Particle Data Group (Workman, et al., 2022).

{ }^8 Based on the ratio of the masses of the W and Z bosons m_{\mathrm{W}} / m_{\mathrm{Z}} recommended by the Particle Data Group (Workman, et al., 2022). The value for \sin ^2 \theta_{\mathrm{W}} they recommend, which is based on a variant of the modified minimal subtraction (\overline{\mathrm{MS}}) scheme, is \sin ^2 \hat{\theta}_{\mathrm{W}}\left(M_{\mathrm{Z}}\right)=0.23122(4).

{ }^{\text {II }} This and other constants involving m_\tau are based on m_\tau c^2 in MeV recommended by the Particle Data Group (Workman, et al., 2022). atomic mass constant and u is the unified atomic mass unit. Moreover, the mass of particle X is m(X)=A_{\mathrm{r}}(X) \mathrm{u} and the molar mass of X is \

(M(X)=A_{\mathrm{r}}(X) M_{\mathrm{u}}\), where M_{\mathrm{u}}=N_{\mathrm{A}} \mathrm{u} is the molar mass constant and N_{\mathrm{A}} is the Avogadro constant.

{ }^{* *} The entropy of an ideal monoatomic gas of relative atomic mass A_{\mathrm{r}} is given by S=S_0+\frac{3}{2} R \ln A_{\mathrm{r}}-R \ln \left(p / p_0\right)+\frac{5}{2} R \ln (T / \mathrm{K}).


66.25: Fundamental Physical Constants — Extensive Listing is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by LibreTexts.

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