Untersuchung der Wachstumssequenzen kleiner Cluster


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LÖFFLER, Peter, 1999. Untersuchung der Wachstumssequenzen kleiner Cluster

@phdthesis{Loffler1999Unter-4668, title={Untersuchung der Wachstumssequenzen kleiner Cluster}, year={1999}, author={Löffler, Peter}, address={Konstanz}, school={Universität Konstanz} }

Untersuchung der Wachstumssequenzen kleiner Cluster deposit-license Löffler, Peter Within the scope of this thesis the structures of small clusters of salts as well as of C60 have<br />been determined.<br /><br />Although the solid phase of cesium salts is the CsCl-structure, only CsCl- and CsI-clusters<br />with NaCl-structures have been found within former experiments. Consequently, there must<br />be a transition from NaCl- to CsCl-type at a certain cluster size or within a certain size range.<br /><br />In order to find this transition, structures of NaI-, CsCl- and CsI-clusters have been determined<br />by measuring their ion mobility: cluster ions are pulled through a drift cell filled with helium<br />(p=2mbar) by a weak electric field (typ. E=10V/cm). The scattering cross section can be<br />calculated from the drift velocity and thus the geometric structure of the clusters can be<br />obtained.<br /><br />From the experiments on positive and negative CsCl cluster ions as well as positive CsI<br />cluster ions growth sequences similar to those of sodium salt clusters were obtained,<br />indicating growth as NaCl-type structures. However, there was one exception, namely the<br />clusters with size n=33. Their mobility can only be explained by assuming that these clusters<br />have CsCl solid like structure.<br /><br />The structures of some clusters made of C60-molecules are still not well known, as there are<br />differences between theoretical predictions and experimental findings. Therefore mobilities of<br />(C60)n clusters were measured within the size range from n=1 to 20.<br /><br />Interpreting these data, one must consider that helium atoms scattering from concave sites<br />on these clusters can undergo multiple collisions. The experimental findings for small (C60)n<br />clusters agree well with the extended theoretical model. However, differences occurred for<br />larger clusters, probably because the intermolecular distance of the C60 molecules is not well<br />known. Nevertheless, the suggested structure of (C60)13, an icosahedron, could be confirmed. Experiments on the Growth Sequences of Small Clusters Löffler, Peter application/pdf 2011-03-24T14:49:25Z 2011-03-24T14:49:25Z 1999 deu

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