Mass absorption coefficients, table

The use of mass absorption (attenuation) coefficients has been discussed throughout this text, especially with regard to the calculation of primary and secondary absorption, interelement correction coefficients, and the fimdamental parameters method of quantitative analysis. Unfortunately, at this time no single, convenient, authoritative table of mass absorption coefficients is available. Variations between the data given in published mass absorption coefficient tables may be large and often depend upon the source and manner of obtaining and refining the data (either experimental or mathematical). Table A2.1 illustrates some variations of mass absorption coefficients as a function of the data source, and this is typical of most of the published data. 

Table 7.8 Mass Absorption Coefficients for Ka., Lines and WLa-, Line...

Table 7.8 contains values of p,/p for the common target elements employed in X-ray work. A more extensive set of mass absorption coefficients for K, L, and M emission lines within the wavelength range from 0.7 to 12 A is contained in Heinrich s paper in T. D. McKinley, K. F. J. Heinrich, and D. B. Wittry (eds.). The Electron Microprobe, Wiley, New York, 1966, pp. 351-377. This article should be consulted to ascertain the probable accuracy of the values and for a compilation of coefficients and exponents employed in the computations. 

TABLE 7.8 Mass Absorption Coefficients for Kai Lines and W Lai Line (Continued)... 

The values of r and a in Table 4-2 show that photoelectric absorption generally makes the greater contribution to the mass absorption coefficient. Absorption leading to scattering, which will be discussed in the next section, gains in relative importance as atomic number Z and wavelength X decrease. 

Effective wavelengths have been included in Table 3-1 to show the changes that occur in this important variable when one gas is substituted for another. These wavelengths correspond to mass absorption coefficients calculated from Equation 3-14 and were obtained by interpolation from tabulated values of absorption coefficients for different wavelengths.15... 

The concordance of the results in Figure 6-2 with the known mass absorption coefficients of iron may be judged from Table 6-1. 

Inspection of the table shows that the quotient a/Wj e is in fact nearly constant that I changes much less rapidly than W e] and that the critical depth has doubled when the highest oxide is reached. All three conditions are reflections of the (positive) absorption effect that occurs in this binary system when iron is replaced by oxygen, which has a lower mass absorption coefficient. 

Table 3.3 Mass fractions and mass absorption coefficients for Ci6ioH3624NnoFePioiF606...

Table B.l Mass absorption coefficients for the 14.41-keV Mossbauer radiation of Fe...

The photoelectric mass absorption coefficients of these polymegs and of poly(methyl methacrylate) PMMA at 8.3 X and 13.3 + A are shown in Table II. These coefficients were calculated using relation (8) and the data listed in Table I. 

Table I. Photoelectric Mass Absorption Coefficients of Halogen Atoms and of Carbon, Oxygen, Hydrogen at 8.34 A (A1 Kali2 emission line) and 13.34 A (Cu Lai. o emission line) (6)...

Table II. Photoelectric Mass Absorption Coefficients of the Halogenated Polymethacrylates and of PMMA...

Example PET. Let us consider polyethylene terephthalate) (PET, C oHK(h n, Ppet=1-35 g/cm3) of tpET =2 mm thickness and an X-radiation wavelength X= 0.15418 nm (CuKa). We set up a table with one row for each chemical element and sum both the masses and the mass absorption coefficients multiplied by the masses. After normalization to the molecular mass of the PET monomer, 192.17 amu, we find (p/p)pet = 1291.97/192.17 cm2/g a value 6.72 cm2/g. Considering the density ppet we find for the linear absorption coefficient Ppet =... 

Table 3 Mass absorption coefficients (cmag-1) in the system...

For a given material of known composition, //, can be calculated using a table that gives the mass absorption coefficients of the elements that constitute that material. After calculating the weighted mass coefficient pM (cm2/g) of the material, it is possible to obtain p = pM p where p is expressed in g/cm3. 

The necessary mass absorption coefficients for the elements are taken from the tables for the particular wavelength used in the analysis in this case Cu Ka. 

We calculated the specific surfaces shown in Table 1 by an improvement of the procedure described in Reference 7. In our more recent studies of coals, rather than using the mass absorption coefficient of carbon, we have computed the mass absorption coefficient of each coal from the elemental composition given by the ultimate analysis. These mass absorption coefficients, which depend quite strongly on the composition and concentration of minerals in the coals, varied from about 7 to 12 cm /gm. We also have taken the values of the coal densities from Fig. 2 of Reference (17). This plot shows the coal density as a function of fixed carbon content and thus provides more reliable densities than the approximation we used in Reference (7). The quantity I A was calculated from the scattering data for colloidal silica samples by the procedure outlined in Reference 7. The proximate and ultimate analyses of... 

In the first place, the absorption of y radiation depends on the density of the absorber, similarly to the absorption of a or radiation. In Table 6.3 the mass absorption coefficients for various absorbers and various energies of y radiation are listed. 

Table 6.3. Mass absorption coefficient fijp in [g/cm ] for y rays of different energy.

Absorption coefficients for all chemical elements are usually tabulated (see Table 2.3) in the form of mass absorption coefficients, p/p (the units are cm /g), instead of the linear absorption coefficients, p. 

Table 2.3. Mass absorption coefficients (in cm /g) of selected chemical elements for the commonly used anode materials. The mass absorption coefficients of the best P-filter...

Absorption means diminution of coherent x-ray intensity in the crystal through inelastic processes such as atomic absorption and fluorescence, photoelectron emission, and Compton effect extinction means intensity diminution due to loss through diffraction by fortuitously oriented mosaic blocks. The simple extinction expression due to Darwin, given in Eq. (18), is only a rough approximation more accurate treatments will be mentioned in what follows. In Eq. (17) the absorption factor is expressed in terms of the linear absorption coefficient /inn (calculated from tabulated values of the elemental atomic or mass absorption coefficients, updated values of which will appear in Vol. IV of International Tables,2 the path length f, of the incident ray from the crystal surface to the point of diffraction r, and the path length t2 of the diffracted ray from that point to the crystal surface. 

Section A3.1 provides details of elemental properties for hydrogen through uranium. The table provides for each element the respective atomic number and weight, the density at STP, the mass absorption coefficients at three selected wavelengths of interest for routine data collection at SR sources and finally the wavelengths of the K and L X-ray absorption edges. 

Table 1 shows the mass absorption coefficients for the hydrogen, carbon, and oxygen components of organic oil, as well as p for sulfur. Because the sulfur p is on the order of ten times greater than those for hydrogen, oxygen, and carbon, the transmission of X-rays are primarily proportional to the sulfur content. 

Values for the mass-absorption coefficient, which is equal to m/p, are listed in standard reference tables. As a first approximation, is proportional to Z A up to the K or L absorption edge thus, the absorption coefficient is dependent on both the element composition and the wavelength of the x-ray (see Fig. 14.14). As mentioned before, there can be one K-absorption edge, three L edges, and five M edges. 

Tables of Wavelengths, 28 Angles, Photon Energies, and Mass-Absorption Coefficients...

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