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Abstract
Preparing an anatase TiO2(101) surface with a high density of oxygen vacancies and associated reduced Ti species in the near-surface region results in drastic changes in the water adsorption chemistry compared to adsorption on a highly stoichiometric surface. Using synchrotron radiation excited photoelectron spectroscopy, we observe a change in the water growth mode, from layer-by-layer growth on the highly stoichiometric surface to bilayer growth on the reduced surface. Furthermore, we have been able to observe Ti3+ enrichment at the surface upon water adsorption. The Ti3+ enrichment occurs concomitant with effective water dissociation into hydroxyls with a very high thermal stability. The water bilayer on the reduced surface is thermally more stable than that on the stoichiometric surface, and it is more efficient in promoting further water dissociation upon heating. The results thus show how the presence of subsurface defects can alter the wetting mechanism of an oxide surface.
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Affiliation(s)
- A Schaefer
- Department of Chemistry and Chemical Engineering, and Competence Centre for Catalysis , Chalmers University of Technology , 41296 Gothenburg , Sweden
| | - V Lanzilotto
- Department of Physics and Astronomy , Uppsala University , P.O. Box 516, SE-75120 Uppsala , Sweden
| | - U B Cappel
- Department of Physics and Astronomy , Uppsala University , P.O. Box 516, SE-75120 Uppsala , Sweden
| | - P Uvdal
- Chemical Physics, Department of Chemistry , Lund University , P.O. Box 124, SE-221 00 Lund , Sweden
| | - A Borg
- Department of Physics , NTNU - Norwegian University of Science and Technology , NO-7491 Trondheim , Norway
| | - A Sandell
- Department of Physics and Astronomy , Uppsala University , P.O. Box 516, SE-75120 Uppsala , Sweden
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Plogmaker S, Terschlüsen JA, Krebs N, Svanqvist M, Forsberg J, Cappel UB, Rubensson JE, Siegbahn H, Söderström J. HELIOS--A laboratory based on high-order harmonic generation of extreme ultraviolet photons for time-resolved spectroscopy. Rev Sci Instrum 2015; 86:123107. [PMID: 26724006 DOI: 10.1063/1.4937463] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
In this paper, we present the HELIOS (High Energy Laser Induced Overtone Source) laboratory, an in-house high-order harmonic generation facility which generates extreme ultraviolet (XUV) photon pulses in the range of 15-70 eV with monochromatized XUV pulse lengths below 35 fs. HELIOS is a source for time-resolved pump-probe/two-color spectroscopy in the sub-50 fs range, which can be operated at 5 kHz or 10 kHz. An optical parametric amplifier is available for pump-probe experiments with wavelengths ranging from 240 nm to 20,000 nm. The produced XUV radiation is monochromatized by a grating in the so-called off-plane mount. Together with overall design parameters, first monochromatized spectra are shown with an intensity of 2 ⋅ 10(10) photons/s (at 5 kHz) in the 29th harmonic, after the monochromator. The XUV pulse duration is measured to be <25 fs after monochromatization.
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Affiliation(s)
- S Plogmaker
- Department of Physics and Astronomy, Molecular and Condensed Matter Physics, Uppsala University, P.O. Box 516, 75120 Uppsala, Sweden
| | - J A Terschlüsen
- Department of Physics and Astronomy, Molecular and Condensed Matter Physics, Uppsala University, P.O. Box 516, 75120 Uppsala, Sweden
| | - N Krebs
- Department of Physics and Astronomy, Molecular and Condensed Matter Physics, Uppsala University, P.O. Box 516, 75120 Uppsala, Sweden
| | - M Svanqvist
- Department of Physics and Astronomy, Molecular and Condensed Matter Physics, Uppsala University, P.O. Box 516, 75120 Uppsala, Sweden
| | - J Forsberg
- Department of Physics and Astronomy, Molecular and Condensed Matter Physics, Uppsala University, P.O. Box 516, 75120 Uppsala, Sweden
| | - U B Cappel
- Department of Physics and Astronomy, Molecular and Condensed Matter Physics, Uppsala University, P.O. Box 516, 75120 Uppsala, Sweden
| | - J-E Rubensson
- Department of Physics and Astronomy, Molecular and Condensed Matter Physics, Uppsala University, P.O. Box 516, 75120 Uppsala, Sweden
| | - H Siegbahn
- Department of Physics and Astronomy, Molecular and Condensed Matter Physics, Uppsala University, P.O. Box 516, 75120 Uppsala, Sweden
| | - J Söderström
- Department of Physics and Astronomy, Molecular and Condensed Matter Physics, Uppsala University, P.O. Box 516, 75120 Uppsala, Sweden
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