Atomic and nuclear properties of materials:
Neptunium (Np)
QuantityValueUnits ValueUnits
Atomic number 93     
Atomic mass [237.0482] g mole-1   
Specific gravity 20.2 g cm-3   
Minimum ionization 1.095 MeV g-1cm2 22.17 MeV cm-1
Nuclear collision length 118.5 g cm-2 5.850 cm
Nuclear interaction length 208.7 g cm-2 10.31 cm
Radiation length 5.87 g cm-2 0.2897 cm
Critical energy 6.57 MeV (for e-) 6.33 MeV (for e+)
Molière radius 18.93 g cm-2 0.9349 cm
Plasma energy 81.22 eV   
Muon critical energy 127. GeV   
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
Note: Since there is no stable isotope, given atomic mass is that of the longest-lived known isotope as of Jan 2007.
Table of isotopes