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Single ionization of simple molecules, e.g. H2, CO2, by fast charged particle impact has been studied using a reaction microscope. By measuring the momenta of the emitted electron and the recoil ionic fragment in coincidence, channel-selective low-energy electron spectra have been recorded. The experimental cross sections will be presented, compared with the predictions of state-of-the-art CDW-EIS calculations and discussed in terms of molecular effects such as (i) autoionization and predissociation channels, (ii) interference patterns resulting from the two-center geometry of the diatomic molecule, in analogy to Young's double-slit experiment and (iii) dependence of the electron emission on the orientation of the molecular axis.

We describe the status of the DESIREE facility, which is an electrostatic ion-storage device consisting of two storage rings with a common section, where ion beams of opposite charges stored in the two rings are merged. The electrostatic storage rings are mounted in a single common vacuum vessel, which is isolated inside an outer vacuum chamber and cooled by means of four cryogenerators. This unique system will allow for studies of interaction among ions of opposite charges at well controlled conditions both in terms of internal degrees of freedom and relative velocity. An advanced ion-beam production system for intense pulses of cold complex molecular ions is also presented.

In this proceedings I will describe the design of a new storage device currently under construction at Stockholm University, Sweden. This device uses purely electrostatic focussing and deflection elements and allows ion beams of opposite charge to be confined under extreme high vacuum and cryogenic conditions in separate "rings" and then merged over a common straight section. This Double ElectroStatic Ion Ring ExpEriment (DESIREE) apparatus allows for studies of interactions between cations and anions at low and well-defined centre-of-mass energies. I discuss the design of the DESIREE facility, highlighting some of the technical advantages of using purely electrostatic over magnetic elements, as well as the issues that have arisen during its development and construction. Finally, the advantages of this design are a boon to fundamental experimental studies and I finish by discussing an example of such potential research.

We are in the process of constructing the double electrostatic storage ring DESIREE at Stockholm University and AlbaNova University Centre. DESIREE with its two 8.8 meters circumference ion storage rings with a common section for tuning the collision energy down to 10 meV will be operated at cryogenic temperatures. The two separate ion source platforms, with maximum floating potentials of 100 keV and 25 keV, respectively, will be equipped with different types of ion sources, e.g. electrospray sources, and equipment for cryogenic cooling of ions before injection in DESIREE. In this poster presentation we will give a status report of the project.

We have studied fragmentation of the hydrated nucleotide anion adenosine 5'-monophosphate after collisions with neutral sodium atoms. Regardless of the initial number (≤ 16) of water molecules attached to the ion, dianion formation always leads to water evaporation as well as loss of a single hydrogen atom, possibly from the adenine part. This damaging effect becomes more important as the number of initially attached water molecules increases, which is just the opposite to the protective behavior observed for collision induced dissociation processes without electron transfer.

We present a systematic study of experimental kinetic energy release distributions for the asymmetric fission processes Cq+60 → C(iq-1 4.

We report on measurements of transfer excitation in collisions of 0.3-1.3 MeV protons with spatially oriented H2 molecules. Evidences of two center interference are found in the angular distribution of the molecule after a transfer excitation process and directly in the projectile angular scattering distributions. These features can be explained in a way which is analogous to that for the interferences in Young's classical double slit experiment: The fast projectiles preferentially capture electrons close to either of the molecular nuclei, and thereby they change their momenta and de Broglie wavelengths. The waves emerging from the two 'slits' of the molecule interfere yielding the observed interference structure.

We have studied the stabilities of multiply charged van der Waals dimers in slow Xe30+ + [C60]2([C60C70], [C70]2) → Xe(30-s)+ + [C60]2r+([C60C70]r+, [C70]2r+) + (r-s)e-electron-transfer collisions (v = 0.4 a.u. and r ≤ 7). The relative ionization cross sections display even-odd variations as functions of r for [C60]2r+, [C60C70]r+, and [C70]2r+. This is in clear contrast to the typical smooth decreasing behavior of the cross sections for multiple ionization of fullerene monomers, which can be explained within the framework of the classical over-the-barrier model. In addition, we report the branching ratios and the kinetic energy releases for the dominant fragmentation processes that yield intact fullerenes. The experimental results are discussed in view of a simple electrostatic model for dimer ionization and recent results from high level density functional theory calculations.