Double ionization Atoms 14 Impact ionization 14 Ionization 14 Helium 10 Sturmian functions 8 Collision problem 4 Double photoionization 4 First Born approximation 4 Fully differential cross sections 4 High-energy electron 4 Ionization of heliums 4 Molecules 4 Particle spectrometers 4 Photoionization 4 Projectile target interaction 4 Projectiles 4 Proton impact 4 Sturmian 4 Transition amplitudes 4 Asymmetric structures 2 Atomic physics 2 Branching ratio 2 Calculations 2 Charged particles 2 Confined atoms 2 Continuum distorted wave-eikonal initial state 2 Continuum problem 2 Convergent close coupling methods 2 Differential cross section 2