Charge equilibrium of fast heavy ions traversing through gaseous media

Abstract

The charge distribution of an incident ion as a function of projectile velocity, its range and its average equilibrium charge are studied theoretically. The calculations are made only for an atomic hydrogen gas target. The charge of the ion is determined by the equilibrium between electron loss from the ion and electron capature from a hydrogen atom to the ion. The charge states of the ions are calculated in two cases; to assume a local balance condition for electron loss and capture and to solve a rate equation for the charge state fraction function under non-local balance conditions, both only taking into account single electron loss and capture processes. In the calculations we use empirical formulae for electron loss and capture cross section by making some simplifications. Calculations for the charge state fraction as functions of ion ranges under non-equilibrium conditions have been carried out in the cases of Ne, Ar, and Xe ions. Calculations for the charge state under local balance conditions have been made in the cases of C, Ne, Ar, Kr, I, and U ions.