Polarisation of a Beam of Electrons by Scattering

Abstract

MOTT¹ has predicted that a polarisation of an electron beam is possible under certain conditions. These conditions are that a fast electron shall be scattered successively by two heavy nuclei through large angles. The intensity of the twice-scattered beam should then depend on its azimuth with respect to the original unscattered beam. Many attempts have been made to detect such an effect, with either negative or inconclusive results; but in none of them have the conditions laid down by Mott all been fulfilled. Chase,² who finds a small positive result, scattered β-rays through 90° from solid targets. The scattering in a solid target is multiple, that is, consists of a large number of small angle collisions, and Mott's theory is completely inapplicable. The same criticism applies to the work of Langstroth,³ who, moreover, uses too small a velocity (due to an error in Mott's paper) for the polarisation to be detectable. In the recent work of Rupp⁴ and Rupp and Szilard the arrangement is still further removed from that considered by Mott.