Measurement of exchange effects in (e,2e) collisions on lithium

Baum G, Blask W, Streun M. Measurement of exchange effects in (e,2e) collisions on lithium. In: Le Journal de Physique IV. Journal de Physique. 4, Proceedings. Vol 9. EDP Sciences; 1999: 219-223.We report on our triple differential electron-atom ionization experiment with resolution of the spin degree of freedom. We use polarized electrons and polarized, low-Z atoms and obtain asymmetries for antiparallel and parallel spin configurations which can either relate to singlet versus triplet scattering or to direct and exchange processes. The spin asymmetry we measure is sensitive to exchange effects between the projectile electron and the active atomic electron. We present: 1) Results for an angular distribution at 54.4 eV incident energy with fixed ratio of shared energies (E-A/E-B = 2.4) which we compare with a DWBA and with the CCC theory. 2) Results for an energy sharing spectrum at 25.4 eV with fixed angles of escape, theta(A) = -theta(B) = 45 degrees, which we compare with a DS3C calculation. Agreement between theory and experiment is in both cases good