The group is involved in research which can be summarized by the following five headings:

Fast collisions between atomic ions and atoms or simple molecules. This experimental research is performed at the internal gas jet target in the cryogenic ion storage and cooler ring 'CRYRING' at Stockholm University. Here, the term 'fast collisions' refers to collisions in which the projectile velocity is larger than the velocity of the active electrons in the target atom or molecule.

Ion fullerene collisions. Under this project we perform experimental studies of electron transfer between slow highly charged ions and single fullerene molecules (typically C60 or C70). These studies are paralleled by developments of simple electrostatic models for electron transfer between conducting or dielectric spheres and the aim is to reduce the seemingly very complex problem of charge transfer from an internally excited many-body system to the simplest possible ingredients. The goals of the experiments are to study electron and energy transfer, the balances between different fragmentation channels with related kinetic energy releases and the ultimate stability limit for fullerenes.

Collisions between slow highly charged ions and fullerene dimers, and/or larger clusters of fullerenes. The clusters of fullerenes are of the van derWaals type and are produced in a cluster aggregation source – a fullerene oven inside a liquid-nitrogen cooled He carrier gas. The clusters of fullerenes, (C60)n, forms a beam where the distribution on n (the number of C60 molecules in the cluster) changes with the oven temperature. In this experiment we study the appearance size as a function of cluster charge state q (the appearance size is the smallest n for which the cluster is stable for a given q). We also measure the ionization cross sections for C60 van der Waals dimers in particular and the related kinetic energy releases.

DESIREE. This Double ElectroStatic Ion Ring ExpEriment is presently under construction. DESIREE is unique in that it may store two beams (e.g. molecular ions of positive and negative charge) and merge them in a few Kelvin temperature environment. Apart from fundamental studies of electron and energy transfer involving complex atomic systems, there are plans for experiments relating to current issues in interstellar chemistry (complex molecules built from simple ones), radiation damage on the individual molecular level.

Modelling of electron transfer in atomic collisions. We have developed a semi-classical model for charge transfer between conducting or dielectric spheres. This model is built on the over-the-barrier concept and it reduces to earlier models for electron transfer in ion-atom, ion-cluster, and ion-surface collisions by letting one or two sphere radii tend to zero/infinity. Possible applications of this model are not yet fully exploited but besides the ones already implemented (electron mobilities within clusters of fullerenes, electron transfer in fullerene-fullerene collisions, and electron transfer in highly charged ion –fullerene collisions) it could be interesting to explore its usefulness in, e.g., colloidal chemistry and cluster surface interactions.
Postal Address: AlbaNova University Center, 106 91 Stockholm, Sweden
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