Atomic and nuclear properties of materials:
Polonium (Po)

Quantity	Value	Units	Value	Units
Atomic number	84
Atomic mass	[208.98243(2)]	g mole-1
Density	9.32	g cm-3
Mean excitation energy	830.0	eV
Minimum ionization	1.141	MeV g-1cm2	10.63	MeV cm-1
Nuclear collision length	114.3	g cm-2	12.27	cm
Nuclear interaction length	200.2	g cm-2	21.48	cm
Pion collision length	137.6	g cm-2	14.76	cm
Pion interaction length	226.7	g cm-2	24.32	cm
Radiation length	6.16	g cm-2	0.6611	cm
Critical energy	7.33	MeV (for e-)	7.06	MeV (for e+)
Molière radius	17.83	g cm-2	1.913	cm
Plasma energy	55.77	eV
Muon critical energy	140.	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, [atomic mass] is that of the longest-lived known isotope as of Jan 2007.
Table of isotopes Warning: may not be current
x ray mass attenuation coefficients