This monochromatic X-ray source comprises a target in particular made from a material incorporating emitting ions comprising an element, the said atoms being excited by electron bombardment, essentially by the electrons located on the K layers of the said atoms. The target material is generally in the solid state and it is held together by means of structuring atoms representing one or more elements and bound to the emitting atoms, the said structuring atoms having an absorption coefficient equal to or lower than 2.3 μm−1 for the X-rays emitted by the emitting atoms.