Potential Energy of highly charged ions
The potential energy is defined as the sum of the binding energies of all missing electrons. Further ionization of electrons increases the potential energy for heavy ions in the range of a few 10 to 100keV.
Fig.1: Potential energy for three different ion species, i.e. Ar (red), Xe (blue) and U (green).
The amount of deposited potential energy can be determined by a calorimetric measurement. By this method it has been found that around 80% of the potential energy is retained in the solid for different charge states of Ar.
Besides calorimetric technics very thin target foils can be used to measure the charge exchange and kinetic energy loss of HCI upon transmission through these foils. We used free-standing 1nm thick carbon nanomembranes and showed that the kinetic energy loss depends also strongly on the charge exchange processes. Also the ions are not neutralized during transmission, thus they deposit only a fraction of their potential energy. The deposition of kinetic and potential energy is therefore closely related.
Fig. 2: Energy loss as a function of charge loss (potential energy loss) for slow highly charged ions transmitted through a 1nm thin carbon nanomembrane.