X-ray line intensities

Luo et al. [83] used an ANN to perform multivariate calibration in the XRF analysis of geological materials and compared its predictive performance with cross-validated PLS. The ANN model yielded the highest accuracy when a nonlinear relationship between the characteristic X-ray line intensity and the concentration existed. As expected, they also found that the prediction accuracy outside the range of the training set was bad. 

Carbyne identification is still a matter of contention since not all identifications are complete and rigorous. They are generally identified by color, hardness, fracture surface, density and XRD, a bulk technique that produces a list of interplanar (hkl) or (/-values [23]. Subtle combinations of (/-values and x-ray line intensity are used for carbyne identification [23] but this approach will fail when using electron diffraction data with an up to... 

Figure 8. Plot of X-ray line intensity ratios for REE La and lower intensity lines (1/lLa), redrafted from Roeder (1985). For the LPi trend line, + = measured intensity of LPi lines, and = LPi intensity eorreeted by subtraction of LP4 interference.

The entire microprobe setup is positioned on a movable granite table. Compound refractive lenses are used for focusing to a routinely achievable spot size of 1-2 pm vertically and 12-15 pm horizontally. The intensity of the incoming, the focused, and the transmitted beam is monitored by ionization chambers and photodiodes. A miniature ionization chamber with an aperture of 50 pm diameter as an entrance window was developed at the ESRF for measuring the intensity of the focused beam close to the sample (Somogyi et al. 2003). The characteristic X-ray line intensities are detected with a Si(Li) detector of 30 mm active area, 3.5 mm active thickness, and 8 pm thick Be window placed at 90° to the incoming linearly polarized X-ray beam. Fast scanning XRF measurements (>0.1 s live time/spectrum) are possible. 

The detected characteristic X-ray line intensity 4meas of element i is expressed as... 

The existing models for emitting x-ray fluorescence intensity of elemental analytical lines from heterogeneous samples are limited in practical applications, because in most publications the relations between the fluorescence intensity of analytical lines elements and the properties of powder materials were not completely studied. For example, particles distribution of components within narrow layer of irradiator which emitted x-ray fluorescence intensity of elements might be in disagreement with particles distribution of components within whole sample. 

When a proportional counter is. used in conjunction with a pulse-height selector, the occurrence of an escape peak may vitiate the results. Assume that the counter filling contains argon, whose K edge is at 3.87 A, and suppose that the pulse-height selector is set to select an x-ray line 3f shorter wavelength the intensity of which is to be measured. This line will excite the K lines of argon. To the extent that these lines are... 

It has always been difficult to do quantitative work with the characteristic x-ray lines of elements below titanium in atomic number. These spectra are not easy to obtain at high intensity (8.4), and the long wavelength of the lines makes attenuation by absorption a serious problem (Table 2-1). The use of helium in the optical path has been very helpful. The design of special proportional counters, called gas-flow proportional counters,20 has made further progress possible, and it is now possible to use aluminum Ka (wavelength near 8 A) as an analytical line (8.10). 

If the intensity of the x-ray line (the analytical line ) were being measured to establish the concentration of an element in a sample, then sc would indicate the highest precision to be expected in this determination. 

The integrated intensity of reflection of an X-ray line from an extended face of a mosaic crystal is4)... 

X-ray Line Wave Length Order Angle of Reflection 100 Estimated Intensity Calculated Intensity for u = 0.235... 

Figure 5.24(B) shows a line profile extracted from the map of Figure 5.24(A) by averaging over 30 pixels parallel to the boundary direction corresponding to an actual distance of about 20 nm. The analytical resolution was 4 nm, and the error bars (95% confidence) were calculated from the total Cu X-ray peak intensities (after background subtraction) associated with each data point in the profile (the error associated with A1 counting statistics was assumed to be negligible). It is clear that these mapping parameters are not suitable for measurement of large numbers of boundaries, since typically only one boundary can be included in the field of view.

Mineral Colour Most intense X-ray lines IR bands (cm 1) Magnetic hyperfine field (T) ... 

Preferred orientation of the particles must be minimized. One of the most effective ways to achieve this is to reduce the particle size by grinding the sample [1], As already discussed in Section III.A, however, grinding can disorder the crystal lattice. Grinding can also induce other undesirable transitions, such as polymorphic transformations [59]. In order to obtain reproducible intensities, there is an optimum crystallite size. The crystallites have to be sufficiently small so that the diffracted intensities are reproducible. Careful studies have been carried out to determine the desired crystallite size of quartz, but no such studies have been reported for pharmaceutical solids [60]. Care should be taken to ensure that the crystallites are not very small, since decreased particle size can cause a broadening of x-ray lines. This effect, discussed earlier (Eq. 9), usually becomes apparent when the particle size is below 0.1 jum. 

Theory Instruments In energy dispersive x-ray fluorescence spectrometry, a sample is bombarded by x-rays that cause the atoms within the sample to fluoresce (i.e., give off their own characteristic x-rays) and this fluorescence is then measured, identified and quantified. The energy of the x-rays identify the elements present in the sample and, in general, the intensities of the x-ray lines are proportional to the concentration of the elements in the sample, allowing quantitative chemical... 

X-ray emission intensities were obtained from the spectra by using a digital filtering method which is available in the standard TN5500 software. For light elements up to, say, bromine, the only lines suitable for analysis are the Ka and K/9 emissions, and the Ka s were used as in the work of Cliff and Lorimer (16). Where overlap occurred between the Ka of one element and the K/9 of another, an experimentally determined correction was used our corrections were in good agreement with those measured by Heinrich et al. (32). 

Figure 4.26 Temperature dependence of (a) the relative X-ray diffraction intensity of high-spin ( TJ and low-spin (Mj) phases of [Fe(4, 7-(CH3)2 phen) (NCSlj] and (b) the high-spin fraction estimated from Mossbauer spectra. In (a) the ordinate represents relative diffraction intensity of lines at 6 = 4.92° and 0...

Phase identification was done on the basis of both d-spacing and the peak height intensity of all the x-ray lines. These values were compared with values obtained for the end-member (unsubstituted) compounds and also calculated by means of the Lazy-Pulverix computer program (9). Precision lattice parameters were obtained by the Debye-Scherrer method with a 114.6 mm dia. camera and filtered Cr Ka radiation standard least-squares methods were used. 

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