Spin Effects in the (e, 2e) Cross Section of Xenon

In a series of experiments investigating the spin-dependent aspects of electron impact induced ionisation of atoms with a spin-resolved incident electron beam we have measured spin-resolved (e, 2e) cross sections for xenon. By experimentally resolving the fine structure levels of the ground state residual ion the existence of an effect analogous to the fine structure effect in excitation has been established, whereby strong and opposite polarisation effects are observed in the ionisation of a spinless closed shell target leading to a fine structure doublet.