Atomic and nuclear properties of materials:
Liquid helium (He) (He)
QuantityValueUnits ValueUnits
Atomic number 2     
Atomic mass 4.002602(2) g mole-1   
Density 0.125 g cm-3   
Mean excitation energy 41.8 eV   
Minimum ionization 1.936 MeV g-1cm2 0.2418 MeV cm-1
Nuclear collision length 51.8 g cm-2 415.1 cm
Nuclear interaction length 71.0 g cm-2 568.4 cm
Pion collision length 79.5 g cm-2 636.2 cm
Pion interaction length 103.6 g cm-2 829.5 cm
Radiation length 94.32 g cm-2 755.2 cm
Critical energy 208.25 MeV (for e-) 203.34 MeV (for e+)
Molière radius 9.60 g cm-2 76.90 cm
Plasma energy 7.20 eV   
Muon critical energy 2020. GeV   
Boiling point @ 1 atm 4.220 K -268.9 C
Index of refraction (@ STP, Na D) 1.02     
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