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Wyszukujesz frazę "Hümmer, K." wg kryterium: Autor


Wyświetlanie 1-2 z 2
Tytuł:
Single-Crystal X-Ray Diffractometry Using Synchrotron Radiation
Autorzy:
Eichhorn, K.
Hümmer, K.
Powiązania:
https://bibliotekanauki.pl/articles/1931648.pdf
Data publikacji:
1994-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
07.85.+n
61.10.Jv
Opis:
The outstanding properties of synchrotron radiation, in particular its high brilliancy over a wide spectral range, its low divergence, its polarization properties, and the pulsed time structure, extend the range of single-crystal X-ray diffractometry to experiments which are not feasible with conventional sources, such as sealed X-ray tubes or rotating anode equipment. Data collection techniques are strongly influenced by the general aims of a diffraction experiment, by the sample quality, its absorption and scattering power, as well as by the reflection profile shape and the instrumental resolution function. Often, the sample properties play a crucial role, and not all samples may be suitable for data collection with synchrotron X-rays. The time-dependence of the primary beam intensity and of its polarization state requires monitoring and normalization to monitor counts, which complicates data collection and data reduction due to sources of both random and systematic errors not known from conventional X-ray sources. There is almost no utilization of X-ray diffraction that cannot profit from the use of synchrotron radiation. X-ray diffraction at a synchrotron radiation source can yield structure factors of an unprecedented quality, provided proper attention is given to sample properties, to data collection strategy and data evaluation procedures. Though little is gained for strong reflections, the improvement is very pronounced for the weaker reflections, including high-order reflections, which can be measured in much shorter time than with conventional X-ray sources. However, synchrotron radiation does not provide a solution to all problems, in some cases conventional laboratory X-ray sources may be more appropriate than synchrotron radiation. Taking into account the limited access to synchrotron radiation sources, X-ray diffraction with synchrotron radiation can only supplement, but not replace conventional X-ray sources and diffraction techniques.
Źródło:
Acta Physica Polonica A; 1994, 86, 4; 497-512
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Experimental Determination of Reflection Phases by Three-Beam Diffraction and its Applications
Autorzy:
Hümmer, K.
Schwegle, W.
Weckert, E.
Powiązania:
https://bibliotekanauki.pl/articles/1920833.pdf
Data publikacji:
1992-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.10.Dp
Opis:
Information on phase relationships between Bragg reflections can be obtained by the interference of Bragg waves. In the three-beam case, phase difference is given by a structure invariant triplet phase relationship. The intensity variation due to the three-beam interaction can be best measured by a ψ-scan experiment. The resulting ψ-scan diffraction profiles scanning through a three-beam position uniquely depend on the triplet phase relationship involved. In principle each three-beam profile is given by a superposition of a symmetrical phase-independent and a phase-dependent profile. Thus, triplet phases can be determined experimentally with an accuracy of about 45 degrees. The ψ-scan method is discussed and some examples of applications to the determination of the absolute structure as well as to the structure determination by combination of measured triplet phases with direct methods are given.
Źródło:
Acta Physica Polonica A; 1992, 82, 1; 83-102
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-2 z 2

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