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.
I usually use the Bethe Bloch equation in the form http://en.wikipedia.org/wiki/Bethe_formula and substitute e^{2}/(4 pi ε_{0}) = r_{e} m_{e}c^{2} where r_{e} is the classical electron radius (2.818 x 10^{-13} cm) and m_{e}c^{2} 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