Asymmetrie des β-Zerfalls und NMR von28Al,38Cl und116In nach dem Einfang polarisierter Neutronen

Polarized²⁸Al,³⁸Cl and¹¹⁶In nuclei have been produced by capture of polarized thermal neutrons. The nuclear magnetic resonance has been observed by measuring the asymmetry of the β-decay. The nuclear magnetic moments were found to be μ(²⁸Al)=2.789(1) nm and μ(³⁸Cl)=2.05(2) nm (uncorrected). The β-decay asymmetry of¹¹⁶In has been observed in superconducting In-metal.     

Ergebnisse von Ballonmessungen an sekundären Elektronen und Photonen

A scintillation counter telescope has been flown in the upper atmosphere at2.4g/cm² from Bergen/Lüneburger Heide for the measurement of electrons and photons of the secondary cosmic radiation. The aim was to get the differential energy spectra of secondary photons in an energy range from 1 to 44 MeV and of secondary and return albedo electrons from 2 to 35 MeV for three different zenith angles (0 °, 90 ° and 180 °). The received photon spectrum is in good agreement to the results of other authors as well to lower as to higher energies. It has been shown, that the spectrum has a great anisotropy with a maximum of intensity around the horizon. The main reason therefore is the atmospheric deepness in the different directions. In this energy range we have found that the Bremsstrahlung of the return albedo electrons is the main reason for the photon flux and secondly the π⁰-decay. The measured electron spectra don't show any significant difference relative to the three zenith angles. These secondary electrons are produced isotropically in the upper atmosphere and they consist of a mixture of secondary and return albedo electrons.     

Quantitative electron probe microanalysis: Uncertainty in the atomic number correction

Summary The atomic number effect in quantitative electron probe microanalysis has been considered from the point of view of error propagation. The results indicate that the chief causes of analysis uncertainty are poorly known electron backscattering factors and mean ionization potential values. Operating variables such as working voltage or X-ray take-off angle cannot be manipulated so as to reduce the effect of the uncertainties. However, the overall analysis uncertainty remains nearly constant over the entire range of working voltages practical for microanalysis.

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Zusammenfassung Der Atomnummerneffekt bei der quantitativen Elektronenstrahlmikroanalyse wurde im Hinblick auf seinen Beitrag zum Analysenfehler untersucht. Danach ist die Hauptursache für den Fehler die Ungenauigkeit der Rückstreufaktoren und der mittleren Ionisationspotentiale. Die Arbeitsbedingungen, wie Abnahmewinkel der Röntgenstrahlung oder Beschleunigungsspannung, können nicht so gewählt werden, daß diese Ungenauigkeit verringert wird. Der gesamte Analysenfehler bleibt jedoch fast über den ganzen für die Elektronenstrahlmikroanalyse üblichen Bereich der Anregungsspannung konstant.