Berlin 2005 – wissenschaftliches Programm
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MO: Molekülphysik
MO 22: Poster I
MO 22.15: Poster
Samstag, 5. März 2005, 10:30–12:30, Poster HU
Melting of Cluster: where do the Magic Numbers come from? — •Christian Hock1, Hellmut Haberland1, Thomas Hippler1, Jörn Donges1, Oleg Kostko1, Martin Schmidt2, and Bernd v.Issendorff1 — 1Department of Physics, University of Freiburg, 79104 Freiburg, Germany — 2Laboratoire Aimé Cotton, CNRS II, 97406 Orsay, France
Melting temperatures of Na clusters show size dependent fluctuations which have resisted interpretation so far. We discuss that these temperatures in fact cannot be expected to exhibit an easily understandable behaviour. The energy and entropy differences between the liquid and solid clusters turn out to be much more relevant paramters. They exhibit pronounced maxima which correlate well with geometrical shell closings, demonstrating the importance of geometric structure for the melting process. Icosahedral symmetry dominates, a conclusion corroborated by new photoelectron spectra measured on cold cluster anions. In the vicinity of the geometrical shell closings the measured entropy is in good agreement with a simple combinatoric model.