[en] In this annual report, the Institut fuer Kernphysik of the university of Frankfurt/Main gives a survey on its scientific activities in the year 1974. Research activities in this period comprised the following fields: nuclear reactions and nuclear structure, heavy ion physics, atomic collision processes, neutron diffractometry and spectroscopy, solid state particle trace detectors, methods of nuclear analysis and mass spectroscopy, ion source development, electronics and data processing, and radiation protection. Furthermore, some application-oriented interdisciplinary research projects were started. (orig./AK)

[en] The paper is concerned with 1. the limits of the kinematical theory 2. basic equations for diffraction 3. Bloch waves 4. band structure and dispersion surfaces of free electrons 5. Weak potential: The two-beam case 6. a modification for X-ray scattering 7. absorption mechanisms and Bormann effect 8. k-selection and boundary conditions 9. the symmetrical laue case 10. the symmetrical Bragg case. (orig.)

[en] Published in summary form only

[en] Liquid water is a non-simple liquid, because on one hand the N particle potential is combined in a non-additive way from the two particle contributions, and on the other hand the pair potential depends on scattering angle and on the relative orientation of the molecules. In this paper, the structure of liquid water is defined in terms of the pair correlation functions gsub(OO), gsub(OH), gsub(HH). Diffraction experiments with X rays, neutrons and electrons allow the pair correlation functions to be determined. The role of electron diffraction is particularly important

[en] We report extensive experiments on the diffraction of very cold neutrons (λ ≅ 100A) at large-area transmission phase gratings with grating constants d=2μm and d=1μm, respectively. The experimental results are compared with Fresnel-Kirchhoff calculations showing agreement in great detail. Using phase gratings it is possible to shift intensities between different diffraction orders, thus making them very useful for other neutron-optics experiments at low energies. Also, the excellent manufacturing precision of our transmission phase gratings meets the requirements for such experiments like very-cold-neutron interferometry. (orig.)

[en] In this chapter attention is focussed on the applicability of diffraction methods in studies of ionic solvation and on methods of analysis of diffraction data by which the structural consequences of ionic solvation phenomena can be quantitatively characterized. The knowledge of the structure of ionic solvation shells is required for the theories attempting to describe ionic solvation on the basis of the potential of interactions. (Auth.)

[en] Published in summary form only

[en] This paper presents an analysis of validity of the Mellin transform when applied to small angle scattering of X-rays or neutrons by a polydisperse set of ellipsoids of revolution. It constitutes a continuation of a previous work performing the same kind of analysis for a set of diffusing particles, consisting of nearly spherical particles. In particular the analysis was focused on the accuracy associated to the size distribution, average radius, total volume of scattering particles as obtained by applying the Mellin transform to the scattering patterns. (orig.)

[en] Diffraction experiments provide information on the Fourier components of microscopic density distributions in crystals. To obtain the spatial densities themselves, an inverse Fourier problem has to be solved. The procedure is complicated by the presence of noise and incompleteness of the data. The application of the maximum-entropy (MaxEnt) principle was a breakthrough in density reconstruction, allowing high-quality density maps to be obtained without involving any a priori information concerning what the reconstructed density should look like. In this work, a procedure is proposed that incorporates a priori (e.g. theoretical) information into MaxEnt reconstructions of spin density distributions. It allows, on the one hand, the evaluation of the existing density models and, on the other, the precise investigation of what new information the experiment brings. Unlike traditional parameter-refinement techniques, the new method does not impose any strict constraints on the density to be reconstructed and is thus much more flexible. At the same time, it suppresses artifacts and yields high-quality density maps. The advantages of the new methods are illustrated by an example of spin density reconstruction based on real polarized neutron diffraction data. (orig.)

[en] The quantitative evaluation is based on a description of the microstructure by numerical data which are derived from models of the lattice configuration and physical conditions of diffraction of the radiation used. Obtained by transformation of the observed intensities, the numerical characteristics depend on the actual microstructure in a complex manner. The procedure for the processing of the experimentally obtained intensity function is described. The spectra provide the lattice parameter value, the average subgrain size, average microdeformation, isotropic microstress, anisotropy parameter, sum of principal stresses, and residual austenite content. (M.D.). 2 tabs., 2 refs