Regensburg 2007 – wissenschaftliches Programm
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DY: Fachverband Dynamik und Statistische Physik
DY 30: Poster II
DY 30.27: Poster
Donnerstag, 29. März 2007, 16:00–18:00, Poster D
Bubble dynamics on laser excited nanoparticles — •Anton Plech1, Vassilios Kotaidis1, Michael Wulff2, Gero von Plessen3, and Christian Dahmen3 — 1Fachbereich Physik, Uni Konstanz, Universitätsstr. 10, D-78457 Konstanz — 2ESRF, BP 220, F-38043 Grenoble — 3I. Physikalisches Institut der RWTH Aachen, Huyskensweg, D-52074 Aachen
Strong nonequilibrium exitation of gold nanoparticles can be achieved by femtosecond laser heating. The nanoscale provides cooling rates of 1013 K/sec in aqueous suspension. Consequently the phase transition in the adjacent water layer is of explosive nature with strong supersaturation. We have employed a pump-probe technique using femtosecond laser pulses as heat stimulus and pulsed x-rays as probe for the nanoscale structure relaxations. By a combination of x-ray techniques it was possible to measure the particle temperature, pressure transients in the water phase, vapor bubble morphology and particle shape. Bubbles expand to sizes in the nanometer range before they recollapse within a subnanosecond interval. The bubble dynamics can be modelled by macroscopic fluid dynamics (Rayleigh Plesset equation) [1]. We found a supersaturation of the water phase to 85 % of the critical temperature [2] as threshold process.
[1] V. Kotaidis, A. Plech: Cavitation dynamics on the nanoscale, Appl. Phys. Lett., 84 (2005) 213102.
[2] V. Kotaidis, C. Dahmen, G. von Plessen, F. Springer, A. Plech: Excitation of nanoscale vapor bubbles at the surface of gold nanoparticles in water, J. Chem. Phys., 124, (2006) 184702.