Atomic and nuclear properties of materials:
Americium (Am)

Quantity	Value	Units	Value	Units
Atomic number	95
Atomic mass	[243.0614]	g mole-1
Specific gravity	13.7	g cm-3
Minimum ionization	1.089	MeV g-1cm2	14.88	MeV cm-1
Nuclear collision length	119.3	g cm-2	8.727	cm
Nuclear interaction length	210.5	g cm-2	15.40	cm
Radiation length	5.80	g cm-2	0.4243	cm
Critical energy	6.50	MeV (for e-)	6.25	MeV (for e+)
Molière radius	18.93	g cm-2	1.385	cm
Plasma energy	66.61	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