Interatomic Coulombic Decay as a New Source of Low Energy Electrons in Slow Ion-Dimer Collisions

We provide the experimental evidence that the single electron capture process in slow collisions between O³⁺ ions and neon dimer targets leads to an unexpected production of low-energy electrons. This production results from the interatomic Coulombic decay process, subsequent to inner-shell single electron capture from one site of the neon dimer. Although pure one-electron capture from the inner shell is expected to be negligible in the low collision energy regime investigated here, the electron production due to this process overtakes by 1 order of magnitude the emission of Auger electrons by the scattered projectiles after double-electron capture. This feature is specific to low charge states of the projectile: similar studies with Xe²⁰⁺ and Ar⁹⁺ projectiles show no evidence of inner-shell single-electron capture. The dependence of the process on the projectile charge state is interpreted using simple calculations based on the classical over the barrier model.