Ejected electron energy distributions for double ionization via direct and rearrangement mechanisms

For multiple ionization of atomic systems by fast projectiles two simple mechanisms may contribute: direct ionization in which each electron is removed by colliding directly with the projectile; and final state rearrangement (e.g., shakeoff) in which the second electron leaves as the target relaxes after the first ionizing event. In the simplest picture the two electrons are uncorrelated. This uncorrelated picture may apply when the first electron leaves quickly. We calculate and compare ejected electron energy distributions in the simple uncorrelated picture for electrons produced by both direct rearrangement mechanisms following ddirect ionization of a first electron. (orig.)