Calculating Bethe Stopping Power Constant: 606,235 or 78,500?

[John2]

The nonrelativistic Bethe stopping power function contains the constant 2*pi*N*e^4 where N is Avogadro's number and e is the electron charge. In the literature, this constant is often calculated to be 78,500. If calculate the constant, I get 606,235 (=2 * pi * 6.02214179E+23 mol^-1 *(1.602176487E-19 C)^4). Does anybody know what my mistake is?

Thank you.

 

[Bob S]

I usually use the Bethe Bloch equation in the form
http://en.wikipedia.org/wiki/Bethe_formula
and substitute

e²/(4 pi ε₀) = r_e m_ec²
where r_e is the classical electron radius (2.818 x 10^-13 cm) and
m_ec² is the electron rest mass
which is 511,000 eV (one of which cancels in the denominator)

See my posts #8 and #9 in thread
https://www.physicsforums.com/showthread.php?t=332899

Bob S

 

[John2]

Thank you. That helped.