Atomic and nuclear properties of materials:
Plutonium (Pu)

Quantity	Value	Units	Value	Units
Atomic number	94
Atomic mass	[244.0642]	g mole-1
Specific gravity	19.8	g cm-3
Minimum ionization	1.071	MeV g-1cm2	21.25	MeV cm-1
Nuclear collision length	119.4	g cm-2	6.020	cm
Nuclear interaction length	210.8	g cm-2	10.62	cm
Radiation length	5.93	g cm-2	0.2989	cm
Critical energy	6.49	MeV (for e-)	6.25	MeV (for e+)
Molière radius	19.36	g cm-2	0.9760	cm
Plasma energy	79.66	eV
Muon critical energy	126.	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