Energy and angle resolved studies of double photo-ionization of helium by electron time-of-flight coincidence spectroscopy

Helium double photo-ionization is studied by a novel coincidence technique which employs time-of-flight spectrometers. Using this technique it is possible to collect simultaneously all the electron pairs, with different energy sharing, emitted by the absorption of a single energetic incident photon. The measurements, in a configuration where the two electrons emerge at 180 degrees relative angle, provide the more complete information on the contribution of the ungerade amplitude to the triple differential cross section and allow the establishment of a relative scale for the full coincident angular distribution measured by other experiments at the same photon energies, but only fora few selected energy-sharing conditions.