Physical and Chemical Constants, and Unit Conversion
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Table 4433. Physical and chemical constants, and unit conversion.

Physical and chemical constants 
Comments
a0 0.0529 nm Bohr radius
c ligh speed in vacuum = 2.99792 × 108 m/s The speed of light in vacuum
P 1.01325 × 105 N/m2 Standard atmosphere
1 barn 10-24 cm2
1 Degree (°) 0.017453293 radian [rad]
1 k 1.38064852 × 10-23 J/K (or m2 kg s-2 K-1) (R/NAVO) Boltzmann constant
1 eV 1.60218 x 10-19 J = 23.053 kcal/mol
1 q 1.6021766208 x 10-19 C Elementary charge
1 kcal/mol 4.184 kJ/mol Or convert with excel file
1 kJ/mol 0.010364512 eV/bond Or convert with excel file
1 NAVO (or N) 6.02214086 × 1023 mol-1 Avogadro's constant
1 MeV/cm 1.602 x 10-11 J/m
1 Pa (pascal) 0.00001 bar = 1 x 10-5 bar Pa is in the SI system.
1 Pa (pascal ) 0.0075006375541921 Torr ≈ 7.5 x 10-3 Torr
1 Pa 1 newton/m2
1 mmHg (10-3mHg) 1 torr
R 1.98719 cal mol-1K-1 = 8.314 J mol-1K-1 Gas constant
1 radian [rad] 57.3 Degree (°)
1 angstrom (Å)  1 Å = 1 x 10-10 m = 1 x 10-4 µm
1 nm   1 x 10-9 m
1 oz 0.00625 lb 
1 g 0.035274 oz
1 kT/q 0.0259 V Thermal voltage at 300 K
1,000 cm-1 0.124 eV  
ε0 8.854 × 10−12 farad/m = 8.85418 × 10−14 F/cm (1/µ0c2) Permittivity of of vacuum
µ0 4π × 10−7 henry/m = 4π x 10−7 N A−2 = 1.25663 × 10−8 H/cm = 4π×10−9 H/cm Permeability of vacuum
h 6.62617 x 10-23 ergs/sec = 6.62617 x 10-34 m2 kg/s = 6.62617 x 10-34 J-s Planck's constant
hc 1239.84 eV nm h: Planck's constant; c: Speed of light.
λ 1.23977 µm Wavelength of 1-eV quantum
λ (nm)
wavelength of radiation Wavelength of photons
g (acceleration due to gravity) 9.8 m s-2  
Atomic mass unit (amu, mu or u) 1.66053906660(50)×10-27 kg  
Electron charge to mass ratio
(-e/me)
-1.7588 x 1011 C kg-1  
Electron classical radius (re) 2.818 x 10-15 m  
Electron mass energy (J) (mec2) 8.187 x 10-14 J = 0.511 MeV  
1 m0 (electron rest mass) 9.1095 × 10−31 kg, or 5.489×10−4 atomic mass units  
Faraday constant (F) 9.649 x 104 C mol-1  
Fine-structure constant (α) 7.297 x 10-3  
Gravitational constant (G) 6.67 x 10-11 Nm2kg-2  
Neutron mass energy (mnc2) 1.505 x 10-10 J = 939.565 MeV  
Neutron rest mass (mn) 1.675 x 10-27 kg  
Neutron-electron mass ratio mn/me = 1838.68  
Neutron-proton mass ratio mn/mp = 1.0014  
Proton mass energy (mpc2) 1.503 x 10-10 J = 938.272 MeV  
1 Mp (proton rest mass) 1.67264 × 10-27 kg  
Proton-electron mass ratio mp/me = 1836.15  
Rydberg constant (r) 1.0974 x 107 m-1  
1 mrad 0.0572958° (degrees)  
2 mrad 0.114592° (degrees)  
3 mrad 0.171887° (degrees)  
5 mrad 0.286479° (degrees)  
9 mrad 0.515662° (degrees)  
10 mrad 0.572958° (degrees)  
20 mrad 1.14592° (degrees)  
50 mrad 2.86479° (degrees)  
100 mrad 5.72958° (degrees)  

 

 

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