beta-NMR Experimente an adsorbierten 8Li unter Verwendung eines Linux basierten Echtzeit-Datenaufnahmesystems
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Philipps-Universität Marburg
Abstract
Within the scope of this thesis beta-NMR experiments were performed
with 8Li adsorbed on two different surfaces. The dissertation consists
of four major parts:
1. a descriptions of the used equipment.
2. due to deficiency concerning the existing data recording system a new
one has been designed and implemented. It is based on a realtime capable
variant of the Linux operating system and uses the framework "ROOT" (cernlib)
for data presentation and analysis. In this thesis the basic architecture
of the new system will be discussed. A more detailed description
of the realtime processes will be given for a special measurement method:
Temperature Programmed Desorption (TPD).
3. beta-NMR Experiments at two opponent directions of polarization
were performed on 8Li adsorbed on the hydrogen terminated silicium(111)
surface. The frequency shift between the resonance curves acquired by
the measurements with two opponent polarisations is near 0. Therefore
the components of the static electrical field gradient of the lithium
binding electron at the nucleus must be 0, too. By means of a simple point
charge model it will be proven, that the adsorbed lithium atom binds to
the silicium atoms of the crystal and not to the hydrogen atoms.
4. the last chapter introduces models for the diffusion of 8Li on a
smooth ruthenium surface and expands the theory on stepped surfaces with
a distinct density of steps. Measurements with the R(001)- and Ru(109) surfaces
were performed, but the interpretation is disputable due to major impurities
by carbon monoxide molecules.
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This item has been published with the following license: In Copyright