(E,2E) COLLISIONS ON XENON WITH SPIN-POLARIZED ELECTRONS

We present measurements of the (e,2e) cross sections of xenon for tran sitions leading to the 5p(3/2) and 5p(1/2) states of the residual ion using an incident polarized electron beam in coplanar asymmetric kinem atics and in the intermediate energy regime. The results show that the spin up-down asymmetry for the 5p(3/2) and 5p(1/2) transitions can be understood as an analogue of the so-called fine-structure effect in i nelastic scattering. However, our present measurements also point to s ignificant contributions from relativistic effects in the electron-ato m system under certain conditions. The measured spin up-down asymmetry is analysed using the density matrix formalism. This approach reveals that different exchange interactions contribute to the fine-structure effect for ionization. The contribution of relativistic interactions in the observed parameters is also investigated by using a semirelativ istic DWBA model to evaluate the scattering amplitudes.