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Berlin 2005 – scientific programme

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O: Oberflächenphysik

O 42: Oberfl
ächenreaktionen II

O 42.6: Talk

Tuesday, March 8, 2005, 12:00–12:15, TU EB407

Energy partitioning in the femtosecond-laser induced Dads + Dads D2 desorption reaction from Ru(001) — •S. Wagner1, M. Rutkowski2, H. Zacharias2, C. Frischkorn1, and M. Wolf11Freie Universtät, Berlin — 2Westfälische Wilhems-Universität, Münster

The energy transfer to different degrees of freedom during the recombinative desorption of D2 from a deuterium covered Ru(001) surface induced by femtosecond-laser excitation has been investigated with (1+1’) resonance enhanced multi-photon photoionization (REMPI) and time-of-flight (TOF) measurements. Rovibrational population distributions of the reaction product are detected via various B 1 Σu+X  1 Σg+ Lyman bands using tunable vacuum ultraviolet (VUV) laser radiation in the excitation step. Rotational quantum states in the vibrational ground state and the first excited state are measured yielding rotational temperatures of Erot /kB=800 K and 1500 K, respectively, at an absorbed laser fluence F of 85 J/m2. Also, a vibrational temperature of the desorbing molecules is extracted which amounts to Evib/kB=1200 K. In addition, comprehensive TOF results (Etrans/kB=2500 K at F = 85 J/m2) enable complete energy balancing and underline the non-thermal and anisotropic energy partitioning during reaction. The effects of multi-dimensional friction between substrate and adsorbate layer and peculiarities of the potential energy landscape governing the D2 recombination are discussed.

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