Effect of Electron Energy Sharing on the Double Photoionization of Helium Near Threshold

Abstract

Energy and angle resolved measurements have been performed in the double photoionization of helium. Whereas the angular distributions do not depend much on the energy sharing $({E}_{1}{,E}_{2})$ at 4 eV above threshold, a strong effect is observed at $E\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}18.6$ eV. These results can be analyzed qualitatively if the total amplitude is split into two parts which are, respectively, symmetric $({a}_{g})$ and antisymmetric $({a}_{u})$ in the interchange of ${E}_{1}$ and ${E}_{2}$, showing that the relative contribution of the latter increases with the excess energy. Dynamical effects of the energy on ${a}_{g}$ are also noticeable in the measurements with equal sharing.