Atomic and nuclear properties of actinium (Ac)
QuantityValueUnits ValueUnits
Atomic number 89     
Atomic mass [227.02775(2)] g mole-1   
Specific gravity 10.07 g cm-3   
Mean excitation energy 841.0 eV   
Minimum ionization 1.112 MeV g-1cm2 11.19 MeV cm-1
Nuclear collision length 117.0 g cm-2 11.62 cm
Nuclear interaction length 205.8 g cm-2 20.43 cm
Pion collision length 140.1 g cm-2 13.91 cm
Pion interaction length 232.1 g cm-2 23.05 cm
Radiation length 6.06 g cm-2 0.6016 cm
Critical energy 7.00 MeV (for e-) 6.75 MeV (for e+)
Molière radius 18.34 g cm-2 1.821 cm
Plasma energy ωp 57.25 eV   
Muon critical energy 134. 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 are no stable isotopes, [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