Berlin 2008 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 49: Particles and Clusters
O 49.5: Vortrag
Mittwoch, 27. Februar 2008, 16:15–16:30, MA 005
Plasmon-induced chaotic photodesorption of xenon from silver nanoparticles on a thin alumina film — •Ki Hyun Kim1, Kazuo Watanabe1, Dietrich Menzel1,2, and Hans-Joachim Freund1 — 1Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany — 2Technische Universität München, 85747 Garching, Germany
We have observed a unique action of plasmon excitations in photodesorption of xenon from silver nanoparticles (AgNPs, ∼8 nm particle diameter) deposited on a thin alumina film. A mass selected time-of-flight method was used to measure the kinetic energy and the total amount of desorbed atoms. The results show that xenon atoms from a xenon monolayer on AgNPs are photodesorbed nonthermally when the laser is tuned to excite the (1,0) mode of the Mie-plasmon of AgNPs (3.5 eV, p-polarization) at low fluences (<∼2 mJ/cm2) where laser induced thermal desorption is negligible. Moreover, the photodesorption yield on plasmon resonance showed chaotic behavior with large bursts and intermittences. These effects were suppressed for multilayers of xenon, which indicates that the nonthermal desorption is not due to thermal heating of the AgNPs.
We suggest a new mechanism of plasmonic desorption by accumulated momentum transfer of the repetitive Pauli repulsions between the collectively oscillating surface electrons and the xenon atom in its shallow physisorption well. The chaotic behavior is ascribed to plasmon coupling which creates fluctuating hotspots and decays slowly (>300 fs) enough to accelerate xenon atoms sufficiently to desorb them.