Atomic and nuclear properties of promethium (Pm)
QuantityValueUnits ValueUnits
Atomic number 61     
Atomic mass [144.91275(3)] g mole-1   
Specific gravity 7.264 g cm-3   
Mean excitation energy 560.0 eV   
Minimum ionization 1.240 MeV g-1cm2 9.008 MeV cm-1
Nuclear collision length 103.5 g cm-2 14.25 cm
Nuclear interaction length 177.7 g cm-2 24.46 cm
Pion collision length 127.5 g cm-2 17.55 cm
Pion interaction length 204.9 g cm-2 28.20 cm
Radiation length 7.51 g cm-2 1.035 cm
Critical energy 9.83 MeV (for e-) 9.49 MeV (for e+)
Molière radius 16.21 g cm-2 2.231 cm
Plasma energy ωp 50.39 eV   
Muon critical energy 180. GeV   
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: Since there is no stable isotope, [atomic mass] is that of the longest-lived isotope known as of Jun 2017.
Table of isotopes via WIKIPEDIA
x ray mass attenuation coefficients from NIST