Atomic and nuclear properties of hydrogen gas (H₂)

Quantity	Value	Units	Value	Units
Atomic number	1
Atomic mass	1.008(7)	g mole-1
Specific gravity (20° C, 1 atm)	8.376E-05	g cm-3
Mean excitation energy	19.2	eV
Minimum ionization	4.103	MeV g-1cm2	3.437E-04	MeV cm-1
Nuclear collision length	42.8	g cm-2	5.115E+05	cm
Nuclear interaction length	52.0	g cm-2	6.210E+05	cm
Pion collision length	70.4	g cm-2	8.406E+05	cm
Pion interaction length	80.3	g cm-2	9.584E+05	cm
Radiation length	63.05	g cm-2	7.528E+05	cm
Critical energy	344.82	MeV (for e-)	338.35	MeV (for e+)
Molière radius	3.88	g cm-2	4.629E+04	cm
Plasma energy ℏωp	0.26	eV
Muon critical energy	3611.	GeV
Melting point	13.81	K	-259.3	C
Boiling point @ 1 atm	20.28	K	-252.9	C
Index of refraction (0° C, 1 atm, Na D)	132.	(n-1)x106

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: The mass of atomic ¹H is 1.007 276 522 6 (13) u (mass of the proton less binding energy of 13.61 eV = 1.461E-09 u).
Table of isotopes via WIKIPEDIA
x ray mass attenuation coefficients from NIST