Three-body quantum dynamics of helium single ionization by 1 GeV/u U92+ impact

We studied fully differential cross sections for single ionization of helium by 1 GeV/u U92+ impact with emission of low-energy electrons (~2–10 eV) in collisions with 'intermediate' momentum transfers (~0.5–1 au). These collisions belong to a new collision regime (for which the basic dynamics of ion–atom collisions have never been explored before) where the impact velocity approaches the speed of light and the minimum momentum transfer is very small, but the ratio of the projectile charge to the collision velocity is of the order of unity. It is shown that higher order terms in the interaction between the projectile and the active target electron do not affect the ionization dynamics. In contrast, the interaction between the projectile and the target core has a profound impact on the shape of the fully differential cross section, changing the binary-to-recoil-peak ratio by two–three times