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- Amann, Peter, et al.
(författare)
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A high-pressure x-ray photoelectron spectroscopy instrument for studies of industrially relevant catalytic reactions at pressures of several bars
- 2019
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Ingår i: Review of Scientific Instruments. - : American Institute of Physics (AIP). - 0034-6748 .- 1089-7623. ; 90:10
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Tidskriftsartikel (refereegranskat)abstract
- We present a new high-pressure x-ray photoelectron spectroscopy system dedicated to probing catalytic reactions under realistic conditions at pressures of multiple bars. The instrument builds around the novel concept of a "virtual cell" in which a gas flow onto the sample surface creates a localized high-pressure pillow. This allows the instrument to be operated with a low pressure of a few millibar in the main chamber, while simultaneously a local pressure exceeding 1 bar can be supplied at the sample surface. Synchrotron based hard x-ray excitation is used to increase the electron mean free path in the gas region between sample and analyzer while grazing incidence <5 degrees close to total external refection conditions enhances surface sensitivity. The aperture separating the high-pressure region from the differential pumping of the electron spectrometer consists of multiple, evenly spaced, micrometer sized holes matching the footprint of the x-ray beam on the sample. The resulting signal is highly dependent on the sample-to-aperture distance because photoemitted electrons are subject to strong scattering in the gas phase. Therefore, high precision control of the sample-to-aperture distance is crucial. A fully integrated manipulator allows for sample movement with step sizes of 10 nm between 0 and -5 mm with very low vibrational amplitude and also for sample heating up to 500 degrees C under reaction conditions. We demonstrate the performance of this novel instrument with bulk 2p spectra of a copper single crystal at He pressures of up to 2.5 bars and C1s spectra measured in gas mixtures of CO + H-2 at pressures of up to 790 mbar. The capability to detect emitted photoelectrons at several bars opens the prospect for studies of catalytic reactions under industrially relevant operando conditions.
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- Ahlund, Mikael, 1959-, et al.
(författare)
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Foreword
- 2015
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Ingår i: Art Bulletin of Nationalmuseum Stockholm. - Stockholm : Nationalmuseum. - 2001-9238. ; 21:2014, s. 9-10
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Tidskriftsartikel (populärvet., debatt m.m.)
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| 8. |
- Ahlund, Mikael, 1959-, et al.
(författare)
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Foreword
- 2014
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Ingår i: Art Bulletin of Nationalmuseum Stockholm. - Stockholm : Nationalmuseum. - 2001-9238. ; 20:2013, s. 9-
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Tidskriftsartikel (populärvet., debatt m.m.)
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| 10. |
- Ahlund, Mikael
(författare)
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Landskapets röster : Studier i Elias Martins bildvärld
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis is about the Swedish landscape painter Elias Martin (1739-1818). The main interest is in his depictions of nature, landscape images and topographical views. Chronologically, it covers the period 1760 to 1810. The first part puts Martin's artistic achievement in a historiographic perspective and presents an overview of his artistic career - from his birthplace Stockholm to Paris and from there to London, where he successfully established himself on the English art scene in the 1770s. Returning to his native Sweden in 1780, he soon emerged as the country's leading landscapist of the period.In the second part of the thesis, a study is presented of Martin's relationship to the art markets of England and Sweden, and in the third an attempt is made, through the medium of a specific genre of Swedish eighteenth-century literature - travel writings - to gain a deeper insight into the attitudes and values of the period. Here, the focus of interest is on different ways of viewing nature and landscape art in Sweden in the late eighteenth century. On the basis of this discussion, an attempt is made to reconstruct a Swedish 'period eye', specific to the upper-class culture of the Gustavian age.These discussions of the importance of the market and of a Swedish period eye form the basis for an answer to the overarching question of this thesis, concerning the relationship between Martin's images and contemporary perceptions of nature. From the conclusions drawn, it becomes clear that different ways of relating to landscape existed side by side. The attitudes discernible in the artist's pictures, as in the travel writings of the period, are diverse and contradictory, complicating an understanding of the eighteenth century's view of nature as something uniform. Elias Martin's art thus illuminates the many vantage points and variations in the Gustavian era's feeling for nature.
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