ROLE OF EXCHANGE SCATTERING IN SPIN-DEPENDENT (E,2E) COLLISIONS

One of the exciting new developments in the field of electron-impact i onization of atoms lies in the use of spin-polarized Electron beams. T he development of new technology which allows one to measure increasin gly differential cross sections is partially motivated by the fact tha t the new results would be expected to serve as a more sensitive test of theory. For the last 20 years, spin-polarized electron-atom scatter ing has provided stringent tests of theory for elastic and inelastic s cattering and the new ionization measurements will undoubtedly extend the horizons for this type of work. Probably the most important issue, however, concerns whether or not these sensitive tests can serve as a probe of new physical effects which were not previously observable. I n this letter, it is demonstrated that the recent measurements of ioni zation of xenon using spin-polarized electrons provide information abo ut exchange effects between the projectile electron and atomic charge cloud which would not be seen using unpolarized beams of electrons.