Empirical relationships for heavy-ion equilibrated charges and charge-changing cross-sections in rarefied hydrogen and their application
Highly ionized heavy evaporation residues (ERs) resulting from heavy ion (HI) fusion-evaporation reactions are knocked out from solid targets to rarefied gas of gas-filled recoil separators. In gas, these ERs undergo charge-changing collisions on their way to a detection system. An equilibrium between the loss of charge (electron capture) and the gain of charge (electron loss) for ionized ERs allows one to use equilibrated charge state distributions in trajectory calculations for ERs moving through a magnetic field. The distance from a target to the point where the ER charge state distributions become to be the equilibrated one is essential for such calculations. This distance can be estimated in simulations based on electron capture and loss cross-sections for energetic HIs. Proper approximations of available experimental data have provided these cross-sections, which were applied to the simulation of the ionic charge evolution for ionized heavy ERs.