Comparative analysis of the threshold behavior of two-electron escape in electron-impact ionization of valence-1 atoms

Using spin-asymmetry data from electron-impact-ionization studies of H, He*, Li, Na, K, and Cs, we determine the energies at which dynamical influences on the inside part of the final-state wave function create detectable departures from the simple Wannier power-law dependence of the cross section on escape energy for the singlet and triplet channels separately. From a comparison of these energies for the six valence-1 systems examined, we conclude that asymmetry measurements provide a window for observing the effects of screening and core polarization on the dynamics of the highly correlated Coulomb three-body breakup.