Berlin 2005 – wissenschaftliches Programm

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O: Oberflächenphysik

O 15: Postersitzung (Adsorption an Oberfl
ächen, Epitaxie und Wachstum, Organische Dünnschichten, Oxide und Isolatoren, Rastersondentechniken, Zeitaufgelöste Spektroskopie, Methoden)

O 15.82: Poster

Freitag, 4. März 2005, 17:00–20:00, Poster TU D

Scaling laws of the angular emission distribution of laser ablated plasma pulses from monoatimic and binary targets in a mass range from 27 to 184 — •Shailendra Nath Srivastava and Klaus Rohr — Technical University of Kaiserslautern, D 67663 Kaiserslautern, Germany

In the present experiment we have investigated emission characteristics of laser produced plasma pulses quantitatively and over a wide mass range. Targets have been monoatomic Al, Ti, Cu, Mo, W and compounds of these with different stoichiometric ratios. Thereby the (average) mass covers a range from 27 to 184. The following major results are observed: (1) The emission cones of all species steepen continuously as a function of the (average) atomic mass. Thereby, for the first time, the widths can be well described by a general scaling law namely k/A + c. Here k and c systematically depend on the size of the ablation area. (2) The measured widths of the compound systems agree with averaged data of its single pure component if the corresponding stoichiometric ratios of the pure targets are used. This suggests that stoichiometry is essentially conserved. (3) All emission shapes can be fitted uniquely by Gauß-functions which reflects the dominating effect of the spatial shape of the laser pulse on the shape of the emission distribution. The result are essential for practical applications, they allows quite simply predictions of emission distributions of monoatomic species hardly to measure otherwise (e.g. gases) and of compound systems of arbitrary compositions.