Atomic and nuclear properties of hydrogen gas (H2)
QuantityValueUnits ValueUnits
Atomic number 1     
Atomic mass 1.008(7) g mole-1   
Specific gravity (20° C, 1 atm) 8.376E-05 g cm-3   
Mean excitation energy 19.2 eV   
Minimum ionization 4.103 MeV g-1cm2 3.437E-04 MeV cm-1
Nuclear collision length 42.8 g cm-2 5.115E+05 cm
Nuclear interaction length 52.0 g cm-2 6.210E+05 cm
Pion collision length 70.4 g cm-2 8.406E+05 cm
Pion interaction length 80.3 g cm-2 9.584E+05 cm
Radiation length 63.05 g cm-2 7.528E+05 cm
Critical energy 344.82 MeV (for e-) 338.35 MeV (for e+)
Molière radius 3.88 g cm-2 4.629E+04 cm
Plasma energy ωp 0.26 eV   
Muon critical energy 3611. GeV   
Melting point 13.81 K -259.3 C
Boiling point @ 1 atm 20.28 K -252.9 C
Index of refraction (0° C, 1 atm, Na D) 132. (n-1)x106     
For muons, dE/dx = a(E) + b(E) E. Tables of b(E): PDF TEXT
Table of muon dE/dx and Range: PDF TEXT
Explanation of some entries
Note: The mass of atomic 1H is 1.007 276 522 6 (13) u (mass of the proton less binding energy of 13.61 eV = 1.461E-09 u).
Table of isotopes Warning: may not be current
x ray mass attenuation coefficients