Near-Threshold Measurements of the Spin Dependence of Electron-Impact Ionization

The spin dependence of the electron-impact ionization of Na has been measured up to 2 eV above threshold with high precision to search for the existence of characteristic oscillations which would support the Coulomb-dipole theory of threshold ionization. The authors have been unable to observe any statistically significant oscillations. The present results are fully consistent with the Wannier theory.