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  • 1
    ISSN: 1432-0630
    Keywords: 79.60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Strained layer GaAs.95P.05 photo cathodes are presented, which emit electron beams spinpolarized to a degree of P = 75% typically. Quantum yields around QE = 0.4% are observed routinely. The figure of merit P2 × QE = 2.3 × 10−3 is comparable to that of the best strained layer cathodes reported in literature. The optimum wavelength of irradiating light around 830 nm is in convenient reach of Ti:sapphire lasers or diode lasers respectively. The cathodes are produced using MOCVD-techniques. A GaAs.55P.45-GaAs.85P.15 superlattice structure prevents the migration of dislocations from the substrate and bottom layers to the strained overlayer. The surface is protected by an arsenic layer so that no chemical cleaning is necessary before installation into vacuum. The source of polarized electrons attached to the Mainz race track microtron MAMI works with such cathodes now. More than 1000 hours beamtime have been performed successfully.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 4 (1971), S. 381-387 
    ISSN: 1612-1112
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenrassung Es wird die Kopplung von hochauflösenden Glaskapillarsäulen mit einem Massenspektrometer beschrieben, wobei auf jede Art von Seperator oder Stromtrennung verzichtet wird. Es zeigt sich, daß die gaschromatografische Trennung voll erhalten bleibt, und daß sich das Massenspektrometer als ein äußerst empfindlicher Detektor erweist, da die gesamte eluierende Substanz zur massenspektrometrischen Indentifizierung zur Verfügung steht. Der Vorteil eines Kleincomputers für die Datenaufnahme und Datenreduktion bei der massenspektrometrischen Aufnahme eines komponentenreichen Gas-Chromatogramms wird demonstriert.
    Abstract: Résumé Le couplage de colonnes capillaires à haut pouvoir séparateur avec un spectromètre de masse est réalisé sans aucun intermédiaire tels que séparateurs ou diviseurs. De cette manière la totalité du composé élué atteint la source d'ions et est ainsi disponible pour l'identification par spectrométrie de masse. On montre que grâce à ce couplage la “résolution” du chromatogramme est conservée et que le spectromètre de masse devient un détecteur trés sensible. L'utilité d'un petit ordinateur pour l'acquisition et la réduction des données de l'ensemble des informations provenant d'un chromatogramme complexe est démontrée.
    Notes: Summary The coupling of high resolution open tubular glass columns to a mass spectrometer is achieved by avoiding any interfaces like seperators or splitting devices. In this way all the effluent without any loss is reaching the ion source and is available for mass spectrometric identification. It is shown that by this coupling the gas chromatographic resolution is fully retained and that the mass spectrometer proves to be a most sensitive detector. The usefullnes of a low cost computer for data aquisition and data reduction of the wealth of information inherent in a multi component chromatogram is demonstrated.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Naturwissenschaften 30 (1942), S. 148-148 
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Naturwissenschaften 31 (1943), S. 505-506 
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1434-601X
    Keywords: 41.50.th ; 41.60.−m
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The interference of transition radiation coherently produced from a periodic stack of four polyimide foils of 7.2 μm thickness and a separation of 162 μm was investigated. This stack has been brought into the low emittance (3 π nm rad) electron beam of the 855 MeV Mainz Microtron MAMI. Transition radiation was observed in the energy range from 2 to 15 keV with a LN2-cooled pin photodiode. A good energy resolution of 0.8 keV and angular resolution of 0.15 mrad was achieved simultaneously allowing for the first time to quantitatively study the interference pattern. Good agreement with theoretical calculations is found. Prospects to exploit transition radiation in the x-ray region from a low emittance electron beam as a high brilliant radiation source are discussed.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Near threshold photoproduction ofη-mesons from the proton has been measured at the MAMI accelerator with the TAPS spectrometer. The mass of theη-meson was deduced from the threshold energy forη-photoproduction. The result of m η =(547.12 ± 0.06 ± 0.25) MeV supports the low value of theη-mass reported from a dp →3Heη measurement at SATURNE in 1992. Theη-decay branching ratio Γ3π0/Γγγ was measured to be (0.832±0.005±0.012).
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die Anwendung von linear-temperaturprogrammierten Capillarsäulen zur Auftrennung von Pyrolyseprodukten wird am Beispiel der Pyrolyse von verschiedenen Polyäthylenproben beschrieben. Es wird ferner gezeigt, da\ die Methode der hydrierenden Pyrolyse-Gaschromatographie ebenfalls in Verbindung mit Capillarsäulen mÖglich ist und zur Identifizierung von bei der Pyrolyse entstandenen ungesättigten Verbindungen verwendet werden kann. Auf Grund der gewonnenen Ergebnisse konnte ein Schema fÜr den thermischen Abbaumechanismus des Polyäthylens aufgestellt werden. Weiterhin ist es mÖglich, im Pyrolyse-Chromatogramm unterschiedliche Verzweigungsgrade von Polyäthylenen zu unterscheiden.
    Notes: Summary The advantages of the use of programmed temperature open tubular columns for the separation of the pyrolysis products of polymers is again demonstrated, using polyethylene samples. It is also shown that the combination of pyrolysis-gas chromatography with subsequent hydrogenation of the thermal breakdown products using open tubular columns for separation can successfully be used in the identification of the unsaturated components formed during pyrolysis. Based on the obtained results, the schematic of the thermal breakdown mechanism of polyethylene could be established. It is further proved that the investigation of the Chromatographic pyrolysis pattern permits an evaluation regarding the degree of branching in the original polyethylene molecules.
    Type of Medium: Electronic Resource
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