Soft X-ray spectroscopy of clusters, surfaces and interfaces

Free Ions

Most of the matter in the universe exists in its ionized form, e.g., in stars, stellar atmospheres or nebulars. Also in the outer atmospheres of planets as the earth, ions are of great importance. Furthermore, the properties of ions are very importand in plasmas, i.e., in nuclear fusion reactors.

However, ions are very reactive and can be produced only in small amounts. Due to theier charge, they repell each other, so the maximum density in the laboratory is usually limited by the so called space charge limit to 108 ions/cm3. One has to compare this to the density of a solid (1023 atoms/cm3) or a gas at a pressure of 1bar (1019 atoms/cm^3). Thus, 108 particles/cm3 corresponds to a pressure of 10-8 mbar. Unfortunately, in many ion experiments even such low densities can not be achieved and the partiell pressure is only in the order of 10-11 mbar. This equivalent to 1-10 atoms per mm3, which is the typical upper limit of the focal size of a x-ray beam.

To perform experiments within an ion beam, we have developed together with groups from the University of Gießen (A. Müller and S. Schippers), University of Frankfurt (R. Dörner) and the FU Berlin (E. Rühl) within the framework of a BMBF collaboration the Photon-Ion-Spectrometer at PETRA III (PIPE).

Photoelectron spectroscopy on free cluster ions using FLASH is performed within a collaboration with the group of K.H. Meiwes-Broer from the University of Rostock. A more detailed description of this setup can be found here.

The Photon-Ion-Spectrometer at PETRA III (PIPE)

 

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