Scattering of Fast Electrons in Gases

Abstract

When sufficiently fast electrons are scattered elastically by atoms, it is possible to regard the effect as being due to the nuclei alone, the atomic electrons playing only a negligible part. The criterion which will allow such a simplification to be made is that the collision parameter for a deflection of an incoming electron by the nucleus must be small compared with the distance between the nucleus and the nearest atomic electron. When this is the case, the observed scattering should be that predicted by the Rutherford scattering formula. Kuper has recently made an experimental investigation of the scattering of electrons of energy above 49,000 volts by helium, neon and argon. His results for helium can be accounted for on the viewpoint proposed, viz., that the nucleus is almost entirely responsible for the observed scattering and that, to a first approximation, the scattering is simple Rutherford scattering. The wave-mechanical formula, which takes into account the effect of the atom as a whole does not give as good agreement with Kuper's results for helium as the Rutherford scattering formula.