Regensburg 2013 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 36: Poster Session II (Organic films and electronics, photoorganics; Nanostructures; Plasmonics and nanooptics, Surface chemical reactions and heterogeneous catalysis, Surface dynamics )

O 36.89: Poster

Dienstag, 12. März 2013, 18:15–21:45, Poster B2

Time-resolved desorption of Hydrogen isotopes from HOPG by femtosecond laser pulses — •Robert Frigge and Helmut Zacharias — Physikalisches Institut, Universität Münster, Germany

The desorption of atomic hydrogen isotopes from HOPG is examined after surface excitation with fs-laser pulses at λ = 400 nm. Desorbed neutral H atoms are ionized using (2+1) REMPI via the 2s ← 1s transition, and are detected with a time-of-flight mass spectrometer. Velocity distribution measurements result in three maxima for fast, medium and very slow desorbed hydrogen atoms. By electron scattering calculations [1] of the vibrational excitation of the H-C bond the three maxima can be identified with different adsorption potentials, depending upon the neighboring H atom position on the graphene lattice. A nonlinear fluence dependence of the desorption yield allows two pulse-correlation experiments. As a result we derive a pulse-delay dependent yield with a FWHM of between 700 fs for the fast and about 1 ps for the slow desorbing atoms . These correlation times indicate short lifetimes of the excited electrons and support a calculation in the DIMET model.
 [1]R. Frigge et al., Phy. Rev. Lett., 104, 256102 (2010)