Comment on charged-particle scattering in dilute and dense plasmas in the presence of intense electromagnetic radiation

It is shown that the quantum theory in the Born approximation gives the classical result when scattering of electrons in the presence of a radiation field occurs in a time short with respect to the period of the radiation. It is argued that the result of Bunkin and Fedorov may be used only when the collision frequency of the electrons in a plasma is much smaller than the frequency of the electromagnetic radiation.