Regensburg 2016 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 14: Surface Chemical Dynamics
O 14.2: Vortrag
Montag, 7. März 2016, 15:15–15:30, S053
Long-lived reactive trapped electrons on amorphous ice surfaces — •Sarah King1, Daniel Wegkamp1,2, Michael Meyer1, Martin Wolf1, and Julia Stähler1 — 1Department of Physical Chemistry, Fritz Haber Institute of the Max Planck Society, Faradayweg 4-6, 14195 Berlin, Germany — 2ICFO - Institute of Photonic Sciences, Mediterranean Technology Park, Av. Carl Friedrich Gauss 3, 08860 Castelldefels (Barcelona), Spain
Trapped electron states have been observed for the first time at the amorphous solid water (ASW)/vacuum interface with relaxation times fourteen orders of magnitude longer than previously observed in bulk ASW. The formation, relaxation and decay pathways, and reactivity of trapped electrons was investigated using time-resolved two-photon photoemission of ≳15 bilayers of D2O on the Cu(111) surface. We find that the decay time of the trapped electron is 15.74 ± 0.12 s, independent of ASW thickness, suggesting an electron hopping mechanism, as opposed to tunneling, for electron recombination with the Cu surface. An increase in the ASW/Cu effective work function of approximately 0.5 eV, concomitant with a decrease in the photo-stationary trapped electron population, is also observed upon repeated irradiation of the ASW/Cu surface with ultraviolet femtosecond pulses. This is consistent with a reaction between the trapped electrons and the ASW at the vacuum interface producing an anionic species, and highlights the possible role of these trapped electrons as reactive intermediates.