Theorie und Praxis der Vakuumtechnik

Wutz, Max; Adam, Hermann; Walcher, Wilhelm

doi:10.1007/978-3-322-87814-4

Cited by 33 publications

(16 citation statements)

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“…3 (bottom) the corresponding profiles are shown for a tube inlet pressure of 1000 mbar. Given the dimensions (length and diameter) of the tube and the inlet pressure applied, one expects a chocked flow for the gas passing the tube, 19 with the pressure at the tube exit being only a function of inlet pressure.…”

Section: Methodsmentioning

confidence: 99%

“…By taking into account the geometrical and instrumental constraints (i.e., the maximum working distance of the electron energy analyzer of 40 mm and the detection area of the analyzer of 1.5 mm in diameter), the aperture sizes, distances, and pumping speeds were dimensioned in such a way as to achieve optimal conditions (see, for example, Ref. 19).…”

Section: Chamber Design Criteria and Differential Pumpingmentioning

confidence: 99%

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New setup for in situ x-ray photoelectron spectroscopy from ultrahigh vacuum to 1mbar

Pantförder

Pöllmann

Zhu

et al. 2004

Review of Scientific Instruments

101

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In an effort to extend the pressure range for electron-based spectroscopies from ultrahigh vacuum into the so-called pressure gap region, we have built a new apparatus for in situ x-ray photoelectron spectroscopy up to 1mbar. The principle of the experimental setup is based on a modified hemispherical electron energy analyzer, a modified twin anode x-ray source, and several differential-pumping stages between sample region and electron detection. The reaction gas is provided in situ either by background dosing or, as a new feature, by beam dosing, using a directed gas beam from a small tube. The latter allows for higher local pressures. The performance of the new setup is discussed, deriving normalization procedures from the analysis of the attenuation of the substrate photoemission intensity by the increasing gas phase pressure. In addition, the change of the work function due to changes in surface composition can be evaluated in situ by analyzing the binding energy shift of the gas phase core-level peaks. As a first study, measurements for the pressure dependence of CO adsorption on Pd(111) between 5×10−8 and 1mbar are presented.

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Section: Methodsmentioning

confidence: 99%

Section: Chamber Design Criteria and Differential Pumpingmentioning

confidence: 99%

New setup for in situ x-ray photoelectron spectroscopy from ultrahigh vacuum to 1mbar

Pantförder

Pöllmann

Zhu

et al. 2004

Review of Scientific Instruments

101

View full text Add to dashboard Cite

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“…The minimum or critical capillary pressure is reached at the capillary exit, where the gas velocity reaches sonic speed. This critical pressure is calculated using eq 2 to be roughly 200 mbar [34]. Within the capillary, the gas velocity increases significantly with the decreasing pressure.…”

Section: Case 1: Oxidation Via Direct Addition Of O( 3 P) and Oh Tomentioning

confidence: 99%

Evidence of neutral radical induced analyte ion transformations in APPI and Near-VUV APLI

Kersten

Funcke

Lorenz

et al. 2009

J. Am. Soc. Mass Spectrom.

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We report on the reactions of neutral radical species [OH, Cl, O(3P), H], generated in a typical atmospheric pressure ionization (API) source upon irradiation of the sample gases with either 193 nm laser radiation or 124 nm VUV light, the latter commonly used in atmospheric pressure photoionization (APPI). The present investigations focus on the polycyclic aromatic hydrocarbon pyrene as representative of the aromatic compound class. Experimental results are supported by computational methods: simple kinetic models are used to estimate the temporal evolution of the concentrations of reactants, intermediates, and final products, whereas density functional theory (DFT) energy calculations are carried out to further elucidate the proposed reaction pathways. The neutral radicals are generated upon photolysis of background water and oxygen always present in appreciable mixing ratios in typical API sources. Substantial amounts of oxygenated analyte product ions are observed using both techniques. In contrast, upon atmospheric pressure laser ionization (APLI) with 248 nm radiation, oxygenated products are virtually absent. In addition, kinetic data evaluation yielded a bimolecular rate constant of k = (1.9 +/- 0.9) x 10(-9) cm3 molecule(-1) s(-1) for the reaction of the pyrene radical cation with OH radicals.

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“…This, of course, depends on the species-dependent value of binding energies, and therefore species with high binding energies, such as SO 2 , are expected to show temperature-dependent variations in their abundances in those regions. Additionally, in terms of the SO 2 sublimation temperature of 90 K (Wutz et al 1992) the shift within the contour lines, e.g., of 10 −10 , cf. Figs.…”

Section: Chemical Evolution Along Different Trajectoriesmentioning

confidence: 99%

Transport processes and chemical evolution in steady accretion disk flows

Ilgner¹,

Henning

Markwick

et al. 2004

A&A

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Abstract.We study the influence of mass transport processes on the chemical evolution in a protoplanetary accretion disk. Local transport processes by advection as well as global transport processes by diffusion are taken into account. Concerning the multi-component system only diffusion in the vertical direction was taken into account. Depending on the transport properties, different schemes are explored to couple/decouple the physical and chemical evolution. Our model is based on a simplified description of hydrodynamics in terms of a steady 1+1-D-α-disk model and includes the kinetics of an extended chemical network of about 250 species. We restrict our calculations to the inner planet formation zone within a distance to the central star of 10 AU. Vertical mixing does change the global chemical evolution as it is demonstrated in detail through a discussion of the chemistry of sulphur-bearing molecules. In addition, the influence of the local disk structure on the chemical evolution is analysed. Our results demonstrate that the chemical evolution is influenced globally by mass transport processes. However, in addition to mass transport processes, information about the local conditions, which determine the kinetics, is still needed in order to analyze the chemical evolution.

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Theorie und Praxis der Vakuumtechnik

Cited by 33 publications

References 0 publications

New setup for in situ x-ray photoelectron spectroscopy from ultrahigh vacuum to 1mbar

New setup for in situ x-ray photoelectron spectroscopy from ultrahigh vacuum to 1mbar

Evidence of neutral radical induced analyte ion transformations in APPI and Near-VUV APLI

Transport processes and chemical evolution in steady accretion disk flows

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