On the production of polarized electron beams by spin exchange collisions

A method for obtaining beams of polarized electrons, by transfer of polarization from an atomic beam to a cross-fired electron beam, is investigated using the formalism of the Stokes vector and the interaction matrix. The transfer takes place through the mechanism of spin exchange in elastic collisions, and this effect is discussed together with problems arising from the statistical nature of the transfer process. The theoretical requirements for a workable system are translated into practical terms and details are given of a proposed experiment. This incorporates a device capable of trapping electrons of low energy for periods of a few milliseconds. The system is estimated to yield a pulsed beam of electrons of a few ev energy, with an intensity of about 10-8 A and a polarization approximately equal to that of the atomic beam.