Atomic and nuclear properties of materials:
Protactinium (Pa)

Quantity	Value	Units	Value	Units
Atomic number	91
Atomic mass	[231.03588(2)]	g mole-1
Density	15.4	g cm-3
Mean excitation energy	878.0	eV
Minimum ionization	1.107	MeV g-1cm2	17.02	MeV cm-1
Nuclear collision length	117.6	g cm-2	7.651	cm
Nuclear interaction length	207.0	g cm-2	13.47	cm
Pion collision length	140.6	g cm-2	9.149	cm
Pion interaction length	233.3	g cm-2	15.18	cm
Radiation length	5.93	g cm-2	0.3861	cm
Critical energy	6.77	MeV (for e-)	6.52	MeV (for e+)
Molière radius	18.59	g cm-2	1.209	cm
Plasma energy	70.90	eV
Muon critical energy	130.	GeV
Melting point	1845.	K	1572.	C

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: There is a well-defined terrestrial aboundance for protactinium even though it is radioactive.
Table of isotopes Warning: may not be current
x ray mass attenuation coefficients