XRF signals

Table 7 Comparison of ratio S (XRF signal) to N (noise) and ratio S to D (dose at focal plane) for 241Am and X-ray tube as incident source. Electronic, spectrometric and detector settings are the same for both sources.

Fig. 3.25 Left signal-to-noise ratio (SNR) of the Mbssbauer spectra of a basalt taken with MIMOS II (full SI-PIN detector system black data-points) and MIMOS IIA (1/4 of full SDD system red data-points) respectively. Right XRF spectra of low Z elements measured with MIMOS IIA (SDDs) at —20°C. The Compton scattered 14.4 keV line (at 13.8 keV) and the resonant 14.4 keV Mossbauer line are well separated...

Some analytical methods open possibilities to evaluate more than only one signal (e.g., OES, MS, XRF). In such cases, the relevant signals yAl, yAl>... (the evaluation of each of which corresponds to another analytical procedure, see Fig. 7.1), do have different sensitivities SAAl, SAAl>..., from which the best will be selected, as a rule. 

As noted above, there are several ways of creating an inner shell vacancy which may de-excite via the emission of a characteristic X-ray. XRF uses a primary beam of X-rays, but suffers from the fact that the characteristic X-ray spectrum recorded from a solid sample contains a scattered version of the primary spectrum, increasing the background signal and therefore degrading analytical sensitivity. The use of an electron beam to create inner shell... 

A more detailed examination of the composition of the variously colored enameled areas was then carried out by masking all but the regions under study with double layers of 0.007-in. (0.18-mm) tin sheet of high purity. The tin by itself showed no peaks other than that of tin in the XRF spectrum, even when placed on a copper substrate. Hence the tin masks cannot have contributed to the observed peaks, nor can any of the signals detected have come from areas under the tin masks. Similar masking was performed for regions on the reliquary. 

X-ray fluorescence (XRF) Archaeometric method for measuring element abundances in inorganic materials X-rays are used to excite atoms to fluoresce and emit a characteristic signal for each element. 

The two halogens Cl and Br also provide some interesting pieces of information. Since a high concentration of chlorine prevails in ocean water, but is practically not involved in any diagenetic processes, chlorine can make its way into the XRF sample only by means of pore water extraction. The curve of chlorine shown in Figure 3.29 represents the porosity of the sediment material so precisely that its concentration could be reconstructed. This influence can also be seen in the case of bromine which is, however, overlain by a similar signal of nearly the same intensity as those of the elements Ba, Cu, Ni, Zn which are controlled by organic matter. 

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