The doubly inelastic contribution to electron loss: H0 and He0 (0.5 MeV u-1) in collision with Ar

The authors have measured absolute doubly differential cross sections for electron loss from the simple structured projectiles H0 and He0 in collision with Ar. By counting electrons in coincidence with the individual charge states of the transmitted beam they are able to separate the contributions from projectile ionization and target ionization, thereby showing the importance of events where both projectile and target are ionized in a single collision: the 'doubly inelastic' events. They should like to draw attention to two possible mechanisms within the doubly inelastic channel and give a theoretical description of the dominant one, making a second Born evaluation and including it within the electron impact approximation. This can result in some overprediction of the absolute cross sections. Better numerical agreement is often achieved by calculating only the singly inelastic contribution but the authors' experiments show that such a model is not conceptually correct.