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Properties of highly charged ions
Potential energy
Highly charged ions are characterized by an additional physical property:
Large amount of potential energy is stored in the ion as a result of the ionization process.
The potential energy increases with the degree of ionization. Ions with different
atomic numbers and charge states have different potential energies, i. e. we
can control the potential energy introduced into the interaction processes.
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Potential energy of highly charged Fe and Pb ions
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Strong electric fields
In highly charged ions (HCIs) the strongest electric fields available in any laboratory exist:
1016 Vcm-1 for U91+.
The strong electric fields caused by the charge of HCIs are the basis for the
emerging field of ion-surface interactions.
Small spatial extend of the projectiles
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The size ratio of a hydrogen-like nickel ion
to a neutral hydrogen atom is equal to the size
ratio of the planet neptune to the sun.
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Large secondary ion yield
Large secondary electron yield
High power deposition into the surface
If HCIs interact with the solid surface the deposition of potential energy leads to ultrafast intense electronic excitations.
These interactions result in features on a nanometer scale, such as blisters and craters.
Example: interaction time: 5-10 fs, interaction area: ~ 10 nm2
Power density deposited into the surface: 1012...1014 Wcm-2
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Scenario of the interaction of slow highly charged ions with solid surfaces
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High specific energy gain for ion acceleration
The specific energy gain in ion accelerators increases with increasing ion charge state according to:
linear accelerator: ~ q
cyclical accelerator: ~ q2
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