Gamma ray cross sections from classical plane wave

[pierce15]

I am aware that in classical electrodynamics a metal exponentially attenuates TEM waves. I am wondering if this fact is sufficient to obtain estimates of the cross section of low energy gamma rays in metals. Obviously it would fail for higher energy gamma rays where Compton scattering and pair production dominate.

 

[nbryan5]

No, it is not sufficient to obtain estimates of the cross section of low energy gamma rays in metals because the exponential attenuation of TEM waves is a consequence of the interaction between the wave and the free electrons in a metal, and this interaction does not apply to gamma rays. Low energy gamma ray cross sections can be estimated using calculations based on the Klein-Nishina formula for Compton scattering, which takes into account the relativistic effects that occur when a gamma ray interacts with an electron.