Dresden 2009 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 46: Time-resolved spectroscopies I
O 46.3: Vortrag
Donnerstag, 26. März 2009, 11:00–11:15, SCH A315
Vibrational response of D2O molecules on Ru(001) upon electron injection observed with time-resolved sum-frequency generation — •Christian Frischkorn, Juraj Bdzoch, Jan Zacharias, and Martin Wolf — Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin
Electrons as excess charges in polar solvents result in molecular motion within the solvent to stabilize the new charge distribution known as electron solvation. We employ time-resolved broadband-IR-VIS SFG (sum frequency generation) spectroscopy as a powerfull technique to study the changes in the vibrational spectra of the D2O water layers upon electron injection from a Ru(001) surface. Unlike in time-resolved photoemission experiments where the electron binding energy is traced and the solvent reponse is inferred subsequently, SFG vibrational spectroscopy directly monitors the molecular reorientation induced by the excess charge. If the Ru surface is excited with 266-nm (4.65 eV) photons, excess electrons injected into the adsorbate layer induce –dependent on layer morphology and layer thickness– drastic changes in the vibrational spectra of the OD stretch vibration. While in amorphous ice layers only weak changes are observed, a SFG signal increase by several orders of magnitude (enhancement factor ∼ 103 − 104) is found in crystalline D2O layers. The physical and chemical processes involved will be discussed.