Atomic and nuclear properties of materials:
Helium gas (He)
QuantityValueUnits ValueUnits
Atomic number 2     
Atomic mass 4.002602(2) g mole-1   
Specific gravity (20° C, 1 atm) 1.66E-04 g cm-3   
Mean excitation energy 41.8 eV   
Minimum ionization 1.937 MeV g-1cm2 3.222E-04 MeV cm-1
Nuclear collision length 51.8 g cm-2 3.117E+05 cm
Nuclear interaction length 71.0 g cm-2 4.269E+05 cm
Pion collision length 79.5 g cm-2 4.778E+05 cm
Pion interaction length 103.6 g cm-2 6.229E+05 cm
Radiation length 94.32 g cm-2 5.671E+05 cm
Critical energy 257.13 MeV (for e-) 252.23 MeV (for e+)
Molière radius 7.78 g cm-2 4.677E+04 cm
Plasma energy 0.26 eV   
Muon critical energy 2352. GeV   
Boiling point @ 1 atm 4.220 K -268.9 C
Index of refraction (@ STP, Na D) 35.0 (n-1)x106     
For muons, dE/dx = a(E) + b(E) E. Tables of b(E): PS PDF TEXT
Table of muon dE/dx and Range: PS PDF TEXT
Explanation of some entries
Table of isotopes Warning: may not be current
x ray mass attenuation coefficients