Application of a dc Fano effect polarized electron source to low-energy electron-atom scattering.

A polarized electron source based upon the photoionization of unpolarized Cs atoms by circularly polarized light (Fano effect) has been developed and applied to the study of spin dependence in low-energy electron-atom scattering. Electron intensities of 10 nA with polarizations of 0.63+/-0.03 have been obtained routinely during continuous runs of up to 75 h. Frequent optical reversal of the direction of the longitudinal electron polarization minimizes systematic effects so that helicity dependent electron-scattering asymmetries smaller than 4 x 10(-4) can be measured.