Research objectives and content
Collisions of ions on laser excited atomic targets offer the possibility of "complete" experiments: initial and final states of the collision partners can be determined as complete as quantum mechanics allows. Especially collisions of 'simple' (e.g. bare, hydrogen- or He-like) multiply charged ions on laser excited Li with only three electrons represent dynamical systems which are attractive from a theoretical point of view. Presently large efforts are made to study such few-electron systems theoretically and detailed experimental results can serve to test these theories. We plan to study electron excitation and captt during multicharged ion-Li* collisions. Li* will be state-prepared with polarized laser light, whereby the light polarization and thus the alignment of the excited Li-electron cloud is varied. The final state of the collision system will be observed by analyzing spectral distribution and polarization of the fluorescence light. The results will be compared with theoretical predictions and will thus allow to unravel the collision dynamics. Also from an applied point of view collisions of multicharged ions on laser excited Li* are interesting: light from such collisions is used tor plasma diagnostics in fusion reactors like TEXTOR in Julich or JET in Culham. Li-beams are injected into the plasma to induce charge exchange reactions with ions therein. The resulting light is a 'fingerprint' of the underlying reactions and can be used to determine quantities such as ion densities and temperatures, provided the absolute values of the relevant cross sections are known. Collisions with excited Li* are especially interesting since an appreciable fraction of the injected Li atoms will become excited upon enetering the plasma.
Training content (objective, benefit and expected impact)
The candidate will receive an intensive training in two experimental techniques: (i) operation of modern laser systems (Ar-ion laser, cw dye-laser) including laser stabilization via Doppler-free spectroscopy (ii) spectroscopic measurement techniques with spectrometers in the visible and far ultraviolet spectral range. In cooperation with theorists he will be trained in the application of extended computer codes for the simulation of collision processes, especially with the CTMC (Classical Trajectory Monte Carlo) method. Moreover he will be involved in the implementation of laboratory data into the computer codes of JET (Joint European Torus in Culham/England). Thereby he will learn to work in a large-scale facility. Links with industry / industrial relevance (22)
Presently there is no direct link with industry. However the understanding of electron capture is important in connection with plasma diagnostics and the creation of plasmas in various industrial applications. a