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, P-1\\ and p(2\\), 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(1\\) , p(2\\)) final state sensitively depends on the initial state wavefunction.