The target-density effect in electron-capture processes

The influence of the target density on the electron-capture (EC) processes in collisions of fast ions with atoms and molecules is considered. The partial EC cross sections σn on the principal quantum number n of the scattered projectile, as well as the total σtot = Σnσn values, are calculated for highly charged ions interacting with gaseous and solid targets in the energy range of E = 100 keV u-1 to 10 MeV u-1. It is shown that with the target density increasing, the populations of the excited states of the scattered projectiles, formed via the EC channel, are drastically suppressed due to projectile ionization by the target particles and, as a result, the total EC cross sections decrease by orders of magnitude at low energies, while the reduction is less prominent at high energies