X-ray terms

The Calculation and Interpretation of X-ray Term Values, and the Calculation of Atomic Scattering Factors... 

The screening constants for neutral atoms are constant so long as no additional screening electrons are introduced, as is strikingly shown by the energy screening constant for X-ray term values. But this con-... 

It has been shown1) that a similar treatment can be applied in the interpretation of X-ray term values by correcting for external screening with the aid of size screening constants. After correcting for the spin... 

Fig. 3. Energy screening constants SE as functions of the atomic number Z, compared with

In this calculation use was made of the reduced X-ray term values given by Wentz el1) for elements above silver, and of the K, L, and M term values for light elements given by Mukher jee and Ray2), corrected... 

Fig. 4. Experimental (T0 values. The circles are obtained from X-ray term values corrected for the spin-relativity effect and external screening, the squares from optical ionization potentials.

X-Ray Term Values, Absorption Limits and Critical Potentials, E. C. Stoner, Phil. Mag., 2, 97, 1926. 

Pauling L. and Sherman J. (1932). Screening constants for many-electrons atoms The calculation and interpretation of X-ray term values and the calculation of atomic scattering factors. Zeit. Krist., 81 1-29. 

We shall now investigate the question of how the statements of the atomic theory with regard to the values of the terms are to be corrected in the light of the recognition of the existence of spin. We begin with the simple example of the hydrogen atom, and with the schemes of terms which may be called hydrogen-like (alkali terms, X-ray terms). In Chapter V (pp. 112, 126) we discussed the values of... 

It should be particularly emphasized that the X-ray terms also are well represented for all elements by Sommerfeld s formula. 

The question as to the accuracy with which all optical (and X-ray) terms may be consistently represented by a suitable central field has been examined by E. Fues 3 he arrived at eminently satisfactory results in the case of the arc spectrum of Na and the analogous spark spectra of Mg+ and Al++. 

Sommerfeld1 has used the relativity correction to explain the multiplicity of the X-ray terms and the departures from Mosley s law, (1), (2), and (3), 29. The numerical agreement is surprisingly good throughout the whole periodic system the foundations of the theory are, however, too uncertain to justify its treatment in this volume. 

A corroboration of this conception of the building up of inner electron groups is found (according to Bohr and Coster) in the diagram of the X-ray terms (fig. 16, p. 179), where marked kinks occur in the curves for the values of Z concerned in this process. 

FIGURE 316. William H. Bragg and his son William L. Bragg reversed von Laue s experiment and used x-rays to measure the distances between ions or atoms in crystals (see text), (a) Depicts the conditions for constructive interference of x-rays termed Braggs Law (b) schematic of Braggs s x-ray apparatus (WH. Bragg and W.L. Bragg, X-Rays And Crystal Structure, 4th ed., London, 1924). 

Clinicians who use MRI (and, indeed, in reality, all users who view MRI images as the basis of their studies) are actually less concerned about the signal-to-noise ratio of the data they have than they are about the contrast-to-noise ratio. In X-ray terms contrast is usually defined as... 

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