ENERGY AND ANGLE-RESOLVED STUDIES OF DOUBLE PHOTOIONIZATION OF HELIUMBY ELECTRON TIME-OF-FLIGHT COINCIDENCE SPECTROSCOPY

Helium double photo-ionization is studied by a novel coincidence techn ique 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 energe tic incident photon. The measurements, in a configuration where the tw o electrons emerge at 180 degrees relative angle, provide the more com plete information on the contribution of the ungerade amplitude to the triple differential cross section and allow the establishment of a re lative scale for the full coincident angular distribution measured by other experiments at the same photon energies, but only fora few selec ted energy-sharing conditions.