A study of the pressure profiles near the first pumping aperture in a high pressure photoelectron spectrometer

Kahk, Juhan Matthias; Villar‐García, Ignacio J.; Grechy, Lorenza; Bruce, Paul J.; Vincent, Peter; Eriksson, Stefan; Rensmo, Håkan; Hahlin, Maria; Åhlund, John; Edwards, Mårten O. M.; Payne, David J.

doi:10.1016/j.elspec.2015.08.005

Cited by 26 publications

(20 citation statements)

References 17 publications

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“…The nozzle has an aperture with a diameter of 1 mm and is located at a normal operating distance, which is twice the diameter of the aperture [22,23]. A schematic of the nozzle and the flow configuration is shown in Figure 1a.…”

Section: Resultsmentioning

confidence: 99%

Visualization of Gas Distribution in a Model AP-XPS Reactor by PLIF: CO Oxidation over a Pd(100) Catalyst

et al. 2017

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Abstract:In situ knowledge of the gas phase around a catalyst is essential to make an accurate correlation between the catalytic activity and surface structure in operando studies. Although ambient pressure X-ray photoelectron spectroscopy (AP-XPS) can provide information on the gas phase as well as the surface structure of a working catalyst, the gas phase detected has not been spatially resolved to date, thus possibly making it ambiguous to interpret the AP-XPS spectra. In this work, planar laser-induced fluorescence (PLIF) is used to visualize the CO 2 distribution in a model AP-XPS reactor, during CO oxidation over a Pd(100) catalyst. The results show that the gas composition in the vicinity of the sample measured by PLIF is significantly different from that measured by a conventional mass spectrometer connected to a nozzle positioned just above the sample. In addition, the gas distribution above the catalytic sample has a strong dependence on the gas flow and total chamber pressure. The technique presented has the potential to increase our knowledge of the gas phase in AP-XPS, as well as to optimize the design and operating conditions of in situ AP-XPS reactors for catalysis studies.

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Section: Resultsmentioning

confidence: 99%

Visualization of Gas Distribution in a Model AP-XPS Reactor by PLIF: CO Oxidation over a Pd(100) Catalyst

et al. 2017

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“…Among them, synchrotron-based techniques such as surface X-ray diffraction, X-ray absorption/emission and photoelectron spectroscopy, and "laboratory-based" techniques, such as infrared, Raman and non-linear optical spectroscopies have been recently developed [10].In this context, X-ray photoelectron spectroscopy (XPS) stands as an excellent characterization tool, since it offers elemental and chemical sensitivity, simultaneously measuring local built-in electrical potentials via the detection of rigid photoelectron kinetic energy shifts in both core and valence levels [11][12][13][14][15][16][17]. Due to the high vapor pressure of many liquids of interest, differential pumping schemes have to be used in photoelectron analyzers to minimize the elastic and inelastic scattering of electrons in the gas phase above the liquid side of the junction [18][19][20]. In addition, small sample-to-analyzer aperture working distances (WDs) must be used, for the same purpose [18][19][20].…”

mentioning

confidence: 99%

“…Due to the high vapor pressure of many liquids of interest, differential pumping schemes have to be used in photoelectron analyzers to minimize the elastic and inelastic scattering of electrons in the gas phase above the liquid side of the junction [18][19][20]. In addition, small sample-to-analyzer aperture working distances (WDs) must be used, for the same purpose [18][19][20]. A reasonable trade-off needs to be found between limiting the electron scattering by the gas phase molecules and keeping the pressure at the sample surface above 90-95% of the nominal pressure in the chamber.…”

mentioning

confidence: 99%

“…A reasonable trade-off needs to be found between limiting the electron scattering by the gas phase molecules and keeping the pressure at the sample surface above 90-95% of the nominal pressure in the chamber. Usual WDs (at which the analyzer focus is optimized) are about the diameter of the aperture itself [18][19][20]. Modern state-of-the-art electron analyzers are capable to operate at pressures of and above 30 mbar (the vapor tension of water at room temperature) and at high photoelectron kinetic energies (KEs, up to 12 keV) [11].…”

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Interface Science Using Ambient Pressure Hard X-ray Photoelectron Spectroscopy

et al. 2019

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The development of novel in situ/operando spectroscopic tools has provided the opportunity for a molecular level understanding of solid/liquid interfaces. Ambient pressure photoelectron spectroscopy using hard X-rays is an excellent interface characterization tool, due to its ability to interrogate simultaneously the chemical composition and built-in electrical potentials, in situ. In this work, we briefly describe the "dip and pull" method, which is currently used as a way to investigate in situ solid/liquid interfaces. By simulating photoelectron intensities from a functionalized TiO 2 surface buried by a nanometric-thin layer of water, we obtain the optimal photon energy range that provides the greatest sensitivity to the interface. We also study the evolution of the functionalized TiO 2 surface chemical composition and correlated band-bending with a change in the electrolyte pH from 7 to 14. Our results provide general information about the optimal experimental conditions for characterizing the solid/liquid interface using the "dip and pull" method, and the unique possibilities offered by this technique.Surfaces 2019, 2 79 perturbation of the junction itself. Therefore, several spectroscopic methods based on photon in/photon out or photon in/electron out approaches have been applied to investigate solid/liquid interfaces. Among them, synchrotron-based techniques such as surface X-ray diffraction, X-ray absorption/emission and photoelectron spectroscopy, and "laboratory-based" techniques, such as infrared, Raman and non-linear optical spectroscopies have been recently developed [10].In this context, X-ray photoelectron spectroscopy (XPS) stands as an excellent characterization tool, since it offers elemental and chemical sensitivity, simultaneously measuring local built-in electrical potentials via the detection of rigid photoelectron kinetic energy shifts in both core and valence levels [11][12][13][14][15][16][17]. Due to the high vapor pressure of many liquids of interest, differential pumping schemes have to be used in photoelectron analyzers to minimize the elastic and inelastic scattering of electrons in the gas phase above the liquid side of the junction [18][19][20]. In addition, small sample-to-analyzer aperture working distances (WDs) must be used, for the same purpose [18][19][20]. A reasonable trade-off needs to be found between limiting the electron scattering by the gas phase molecules and keeping the pressure at the sample surface above 90-95% of the nominal pressure in the chamber. Usual WDs (at which the analyzer focus is optimized) are about the diameter of the aperture itself [18][19][20]. Modern state-of-the-art electron analyzers are capable to operate at pressures of and above 30 mbar (the vapor tension of water at room temperature) and at high photoelectron kinetic energies (KEs, up to 12 keV) [11]. The extension of AP-XPS to high photon energies (i.e., high photoelectron KEs) has two main advantages: the reduced photoelectrons/gas molecules scattering provides higher signal intensity at...

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“…The requirement of two aperture diameters can be relaxed somewhat at pressures above around 10 mbar. 40 Other factors that limit the signal, and thus the pressure, are the gas phase photon absorption and the necessary separation of the sample environment from the x-ray/VUV source either by a thin membrane (e.g., Si 3 N 4 ) or differential pumping. 9,10 Gas phase ionizations can overlap ionizations of interest, causing analysis difficulty, but can also be used to detect products or changes in the sample work function.…”

Section: Chemical Sensitivitymentioning

confidence: 99%

UHV and Ambient Pressure XPS: Potentials for Mg, MgO, and Mg(OH)2 Surface Analysis

Head

Schnadt

2016

JOM

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The surface sensitivity of x-ray photoelectron spectroscopy (XPS) has positioned the technique as a routine analysis tool for chemical and electronic structure information. Samples ranging from ideal model systems to industrial materials can be analyzed. Instrumentational developments in the past two decades have popularized ambient pressure XPS, with pressures in the tens of mbar now commonplace. Here, we briefly review the technique, including a discussion of developments that allow data collection at higher pressures. We illustrate the information XPS can provide by using examples from the literature, including MgO studies. We hope to illustrate the possibilities of ambient pressure XPS to Mg, MgO, and Mg(OH) 2 systems, both in fundamental and applied studies.

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A study of the pressure profiles near the first pumping aperture in a high pressure photoelectron spectrometer

Cited by 26 publications

References 17 publications

Visualization of Gas Distribution in a Model AP-XPS Reactor by PLIF: CO Oxidation over a Pd(100) Catalyst

Visualization of Gas Distribution in a Model AP-XPS Reactor by PLIF: CO Oxidation over a Pd(100) Catalyst

Interface Science Using Ambient Pressure Hard X-ray Photoelectron Spectroscopy

UHV and Ambient Pressure XPS: Potentials for Mg, MgO, and Mg(OH)2 Surface Analysis

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