Berlin 2005 – wissenschaftliches Programm

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O: Oberflächenphysik

O 42: Oberfl
ächenreaktionen II

O 42.6: Vortrag

Dienstag, 8. März 2005, 12:00–12:15, TU EB407

Energy partitioning in the femtosecond-laser induced D_ads + D_ads → D₂ desorption reaction from Ru(001) — •S. Wagner¹, M. Rutkowski², H. Zacharias², C. Frischkorn¹, and M. Wolf¹ — ¹Freie 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 Σ_u⁺ ← X  ¹ Σ_g⁺ 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 E_rot /k_B=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 E_vib/k_B=1200 K. In addition, comprehensive TOF results (E_trans/k_B=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.