TABLE OF CONTENTS X-ray methods involve the excitation of an atom by the removal of an electron from an inner energy level, usually from the innermost K level or from one of the three L levels. Atoms can be excited either by direct bombardment of the sample with electrons (direct emission analysis, electron probe microanalysis, and Auger emission spectroscopy) or by irradiation of the sample with x rays of shorter wavelength than analyte elements (x-ray fluorescence analysis). Electron spectroscopy for chemical analysis (ESCA) measures the energy of the electrons ejected from inner electron levels when the sample is bombarded by a monochromatic x-ray beam. In x-ray absorption the intensity of an x-ray beam is diminished as it passes through material. X rays are also diffracted by the planes of a crystal, which provides a useful method for qualitative identification of crystalline phases.
When an atom is bombarded by sufficiently energetic electrons or x radiation, an electron may be ejected from one of the inner levels of the target atoms. The place of the ejected electron is promptly filled by an electron from an outer level whose place, in turn, is taken by an electron coming from still farther out. Each transition is accompanied by the release of an x-ray photon, the energy of which is characteristic of the element from which it originated. The measurement of the various photon energies produced by sample excitation provides a means of identifying its constituent elements. A...
