OBSERVATION OF EXCHANGE IN COLLISIONS OF POLARIZED ELECTRONS WITH ATOMS AND MOLECULES

Exchange collisions of electrons with Hg and Na atoms and O2 and NO mo lecules have been studied by means of polarized electrons for energies between 2.5 and 15 eV and scattering angles up to 110-degrees. While significant exchange effects have been observed for collisions of elec trons with Hg and Na atoms, differential spin exchange cross sections for elastic collisions from the open shell molecules O2 and NO are muc h smaller. This is in agreement with recent theoretical calculations t hat predict significant exchange effects only for oriented molecules. A small but significant spin exchange structure for e-O2 collisions be tween 8 and 15 eV at theta = 100-degrees is attributed to a shallow 4S IGMA(u)- resonance.