Characteristic X-ray photon

Appearance potential methods all depend on detecting the threshold of ionization of a shallow core level and the fine structure near the threshold they differ only in the way in which detection is performed. In all of these methods the primary electron energy is ramped upward from near zero to whatever is appropriate for the sample material, while the primary current to the sample is kept constant. As the incident energy is increased, it passes through successive thresholds for ionization of core levels of atoms in the surface. An ionized core level, as discussed earlier, can recombine by emission either of a characteristic X-ray photon or of an Auger electron. 

Both WDXRF and EDXRF lend themselves admirably to quantitative analysis, since there is a relationship between the wavelength or energy of a characteristic X-ray photon and the atomic number of the element from which the characteristic emission line occurs. The fluorescence intensity of a given element is proportional to the weight fraction. Emitted fluorescence radiation is partly absorbed by the matrix, depending on the total mass absorption coefficient ... 

FIGURE 2.23 Scanning electron microscopic (SEM) picture of silver-montmorillonite. Left side morphology of the sample made by backscattered electrons. Right side silver map made by characteristic x-ray photons. Silver concentration is proportional to the density of the light spots. The arrows show spots with 100% silver concentration. (Reprinted from Konya et al. 2005, with permission from Springer.)... 

The backscattered image is shown on the lower left side of the figure, and a lead distribution map of the same surface obtained by characteristic x-ray photons is shown on the lower right side. On the top figure, the environment of the spot indicated with No. 2 is enlarged. The bright spots on the backscattered image indicate... 

Figure 6.1 Excitation of a characteristic X-ray photon or an Auger electron by a high energy X-ray photon or electron.

Moseley first estabUshed the relationship between the wavelength i of a characteristic X-ray photon and the atomic number Z of the excited element (see Fig. 

True surface analysis on the order of a few atomic layers can be done by a somewhat different mechanism, as illustrated in f igure 20.74. In this case, the characteristic x-ray photon illustrated in Figure 20.73 does not escape the vicinity of the atomic core but instead ejects one of the L shell electrons. The result is a nonradiating electron transition with a kinetic energy characteristic of the chemical element (carbon). 

Figure 2.9 The photoelectric interaction, (a) Before photoelectric interaction a photon of energy E encounters the atom, (b) In the photoelectric interaction the photon is absorbed by a K-shell electron, and the electron is ejected with an energy equal to the photon energy less the K-shell electron-binding energy, (c) the K-shell vacancy is filled by an L-shell electron, and the difference in binding energies is given off as either (c) a characteristic x-ray photon or (d) an Auger electron. (Reprinted by courtesy of EG G ORTEC.)...

The secondary absorption effect is due to interaction of the characteristic x-ray photons excited within the specimen and all types of atoms making up the specimen. The total secondary absorption (Ai)cscV 2 for a given characteristic photon of wavelength Xj from an analyte element i, is given by Eq. (2.33). 

Auger process is an intrinsic energy-loss process in an atom when a characteristic X-ray photon is emitted due to an atomic many-body effects) apart from the diagram lines Kcxi, Kcx2, Kpi, and KP2 (Verma 2000). 

Figure 3.16 (a) Interaction of x-rays with a solid producing atomic excitation with the emission of a photoelectron, (b) followed by de-excitation with the emission of an Auger electron, (c) or by the emission of characteristic x-ray photons. 

The second process by which the excited atom can regain stability is by transfer of an electron from one of the outer orbitals to fill the vacancy. The energy difference between the initial and final states of the transferred electron may be given off in the form of an X-ray photon. Since all emitted X-ray photons have energies proportional to the differences in the energy states of atomic electrons, the lines from a given element are characteristic of that element. The relationship between the wavelength of a characteristic X-ray photon and the atomic number Z of the element was first established by Moseley. Moseley s law is written ... 

For a sample consisting of a thin film (so that proton energy loss and X-ray absorption can be neglected), the yield of characteristic X-ray photons of energy from element Z induced by particles of energy E is given by... 

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