Monochromatic single crystal

The invention concerns a monochromatic single crystal, which consists of a very pure two-component mixture without crystal faults and having a mixing gradient (e.g. germanium-silicon alloy). The two components differ in their crystal lattice constants, so that the crystal has a gradient of the lattice constant in the direction of the mixing gradient, e.g. it changes constantly by about 15%. There is a small bend of the lattice surface at right angles to the mixing gradient. A mono-energetic elementary particle radiation, particularly neutron radiation, can be produced with these crystals which can be used for exact spectroscopic examination (with a monochromator according to Maier-Leibnitz). Alloys such as copper-germanium, copper-aluminium are also suitable for this. (UWI)