The recent developements of the neutron small-angle scattering technique have been reviewed and the results of the invstigations using the same technique especially at Jülich in West Germany and at ILL, Grenoble have been surveyed. At the beginning of this paper the principles and the characteristics of the neutron small-angle scattering have been dicussed in comparison with the X-ray small-angle scattering. Then the two instruments for the neutron small-angle scattering in both Jülich and Grenoble have been briefly described. The optimum conditions for the intensity and the resolution of the instruments which should be taken into account for the design of the instruments have been discussed. The typical applications of the neutron small-angle scattering are reviewed. These are1) the voids caused in Al single crystals by neutron irradition, 2) non-destructive testing of the fatigued turbine blade, 3) magnetic inhomogeneities in Fe-Ni invar alloys, 4) flux-line lattices in type II superconductors, 5) polymers in solid state and 6) biological macromolecule. The possibilities of the future developemeut in this field of investigations are discussed.
Recent studies of the measurements of charge densities in atoms and molecules by means of gas electron diffraction are reviewed. The following topics are described the theoretical background which relates the scattering intensity and the electron density distribution of target molecules and atoms, experimental apparatuses for the intensity measurement of scattered electrons, and comparison of experimental results with theoretical predictions for several simple molecules. A brief survey of the present stage of theoretical achievements and problems on electron scattering is also given.