Staff View
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ISSN:
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1089-7623
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Source:
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AIP Digital Archive
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Topics:
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Physics
Electrical Engineering, Measurement and Control Technology
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Notes:
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A new geometrical criterion is proposed for the optimization of high-resolution electron energy loss spectrometers based on spherical 180° SDA and cylindrical 127° CDA deflector anodes. This criterion concerns the relative geometrical configuration of the electrodes and its application should improve the energy resolution of tandem monochromator-analyzer spectrometers used in high-resolution electron energy loss spectroscopy (HREELS) studies of surfaces. Electron trajectory calculations for both spherical and cylindrical fields show that there exists a tandem configuration for which the electrons are perfectly refocused in position and in energy at the exit of the analyzer. On the contrary, the conventional tandem configuration used in HREELS results in a poorly defined image as a consequence of the optical aberrations of the deflectors. The correction of these aberrations is possible if a modification to the conventional configuration is applied. The new geometry may be achieved by a simple rotation of both the analyzer and the monochromator by 90° in the same sense with respect to the beam axis or by a 180° rotation of the monochromator from the conventional configuration. It is also shown that the adoption of these geometric configurations is consistent with the dispersion-compensation principle if the exit aperture of the monochromator and the entrance aperture of the analyzer are enlarged adequately.
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Type of Medium:
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Electronic Resource
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URL:
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