Abstract: Spin polarized electron source using an emissive micropoint cathode. At least one portion of each micropoint, including the top of the latter, is ferromagnetic, so that the electrons emitted by the cathode are spin polarized in a given direction, when the portion is subject to a magnetic field parallel to the given direction.

Abstract: The invention relates to an apparatus for determining the electron states of a material. This apparatus comprises an enclosure containing a material, means for producing electrons of energy E.sub.i such, that on then penetrating the material, they acquire an energy E.sub.f below E.sub.i, accompanied by an emission of photons having different wavelengths. The apparatus also comprises another enclosure equipped with a tube entering the vacuum enclosure and provided with an entrance slit and another tube provided with a regulatable exit slit. The apparatus also comprises a grating located in the other enclosure and etched with lines, whilst being able to rotate about an axis parallel to these lines in order to select photons of the same wavelength. The apparatus finally has means for detecting the selected photons.Application to the determination of the forbidden band of a semiconductor.