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[en] Cross section calculations of low energy e^- -molecule scattering have been limited to targets with few electrons. We show that the use of soft norm-conserving pseudopotentials in the target description and in the scattering calculations makes possible the study of the low-energy electron scattering by many-electron molecules. We present results for C F₄, C Cl₄, Si Cl₄, Si Br₄ and Si L₄ with 42, 74, 82, 154, and 226 electrons respectively. The pseudopotentials replace the nucleus and the core electrons of each atom so that only the valence is described in a many-body framework. Our calculated cross sections are in good qualitative agreement wit experiment. Except for C F₄, we show theoretical cross sections for these molecules for the first time. For the C F₄ molecule our results are in excellent agreement with the theoretical data available in the literature [8], which is an all-electron calculation, and also with the experimental results [11]. (author)

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[en] Charge transfer is an important process in many astrophysical and atmospheric environments. While numerous experimental and theoretical studies exist for H and He targets, data on other targets, particularly metals and molecules, are sparse. Using a variety of theoretical methods and computational techniques the authors are developing methods to estimate the cross sections for electron capture (charge transfer) in slow collisions of low charge state ions with heavy (Mg, Ca, Fe, Co, Ni and Zn) neutrals. In this ongoing work particular attention is paid to ascertaining the importance of double electron capture

[en] The discovery of the exceptional stability of C₆₀ (Buckminsterfullerene) and its ions has prompted a large number of experimental and theoretical investigations concerning this soccerball-shaped molecule. After the discovery of a method, by which macroscopic quantities of C₆₀ are available, this molecule has become an obvious candidate for structural and dynamic investigations by atomic-collision experiments. In our experiments, the fragment distributions suggest a mechanism where fragmentation occurs by sequential loss of 'pairs' of carbon atoms. We have continued the C⁺₆₀ fragmentation studies and also included negative and multiply charged as well as other fullerene ions besides C₆₀. In the case of positive fullerenes, only even-numbered molecules were observed, but for the negative fullerenes, also odd-numbered molecules were recorded on the ∼ 0.5% level relative to the even-numbered components. This finding indicates that the electron structure also plays an important role for the stability of fullerene ions, or perhaps that negative molecules can exist in some isomeric form. The total destruction cross sections for fullerene ions have been measured in several target gases. We are planning to continue with collisional studies of various fullerene ions with special emphasis on a better understanding of the collisionally induced fragmentation for ions in well prepared states, and also endohedral complexes and fusion will be investigated in collision studies. (EG) (8 refs.)