Double ionization of helium in fast ion collisions: the role of the correlated initial state

The momentum distribution of the electrons emitted in double ionization of helium by 100 MeV u-1 C6+ ions has been obtained in a kinematically complete collision experiment. Attention is focused on the momentum components of the electrons along the projectile axis, p1parallel and p2parallel, which are negligibly affected by the momentum transfer by the projectile. Calculations in the Born approximation including shake-off demonstrate that the correlated two-electron (p 1parallel, p2parallel) final state sensitively depends on the initial state wavefunction. (author)