München 2004 – wissenschaftliches Programm

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MS: Massenspektrometrie

MS 7: Poster

MS 7.6: Poster

Donnerstag, 25. März 2004, 14:00–16:00, Schellingstr. 3

Bimodale Velocity Distribution of Neutral Atoms released from Laser Ablation — •Jochen Maul¹, Klaus Eberhardt², Gerhard Huber¹, Sergej Karpuk¹, Gerd Passler¹, Ilia Strachnov¹, Norbert Trautmann², and Klaus Wendt¹ — ¹Institut für Physik, Staudingerweg 7, 55099 Mainz — ²Institut für Kernchemie, Fritz-Strassmann-Weg 2, 55099 Mainz

Laser ablation and desorption techniques are commonly used in material science and microanalytics. The laser ablation process itself, however, is only partially understood. With increasing laser fluences, e.g., different thresholds are observed, thus turning the process more and more manifold. We present a postionisation analysis of neutral atoms released from a metallic gadolinium target by UV-laser ablation. Using a variable delay between ablation and postionisation, we have investigated the velocity distribution in the ablated plume. The presented results are obtained in the weakest regime directly above the onset for ablation where neutral species are produced exclusively, and also in a higher regime where both ions and neutrals are released. The results can be described by a bimodale structure of the ablation process, involving the prompt release of particles induced by a shockwave, followed by the emission of a thermal vapour.

In order to probe the kinematics of the ablated ions, different kinetic energy classes of the charged species are selected by repulsive electric fields of different duration. Finally, the kinematics of the neutral and of the charged species are compared.