Dresden 2006 – wissenschaftliches Programm

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O: Oberflächenphysik

O 14: Poster session I (Adsorption, Epitaxy and growth, Phase transitions, Surface reactions, Organic films, Electronic structure, Methods) (sponsored by Omicron Nanotechnology GmbH)

O 14.33: Poster

Montag, 27. März 2006, 18:00–21:00, P2

Subnanosecond dynamics of the liquid-vapor phase transition at interfaces — •Florian Lang, Johannes Boneberg, and Paul Leiderer — University of Konstanz, Postfach M 676, Universitaetsstr. 10, 78457 Konstanz, Germany

When a liquid is heated rapidly, the transition to the vapour phase does not occur at the equilibrium boiling temperature, but the liquid rather remains in a metastable superheated state. Only at a distinctly higher temperature evaporation will take place via nucleation or - at sufficiently large superheating - a spinodal process. We have studied here the evaporation process in a liquid film in contact with a solid substrate, which was heated momentarily by a short Nd:YAG laser pulse. The liquid layer (isopropanol, C3H8O) had a thickness of some hundred nanometers. Due to heat transfer, the fluid adjacent to the interface evaporates and the film on top is ejected as an intact liquid layer. The phase transition and the ejection process are monitored by reflectometry with a temporal resolution of about 200 ps and a spatial sensitivity on the nanometer-scale in the direction perpendicular to the substrate. We demonstrate that this approach allows us to determine the generated pressures, the achievable superheating and the relevant timescales of the process and as a consequence provides insights in the nature of the very early stages of the phase transition.