Crystals Analyzing

Crystal Name and Orientation (Miller Indices) 2d-Spacing (nm) Element Range 

TIAP Thallium acid phthalate (100) (Thallium hydrogen phthalate) 2.576 Fe-Na 

and others Multilayered synthetic crystal 5.0-19 Light elements from Be to N, N-AI, Ca-Br depending on the cf-spacing 

In some systems, the rotation of the crystal and the detector is mechanically conpled with gears. Other systems have no mechanical coupling but use computer-controlled stepper motors for the 

Schematic of the optical path in a curved crystai spectrometer. (Courtesy of PANaiyticai, inc., The Netherlands, www.panaiyticai.com.) 

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The use of an analyzing crystal in Method I will eliminate possible interference by diffraction peaks or b characteristic lines of the film. This method, called Method III to preserve the numbering ift the literature,9,10 is well adapted to a spectrograph (4.15) and may thus... 

Owing to the fact that iron Ka has a much lower excitation potential than the corresponding line of either silver or zirconium, it is not possible here to excite the substrate Ka without exciting iron Ka as well. Following are estimated Ka counting rates (counts per second) for the massive metals under the experimental conditions employed iron, 200,000 zirconium, 32,000 silver, 8100. Clearly, Method I would fail here if Ka lines were used Meftiod III is successful because the analyzing crystal eliminates interference by iron Ka. 

The modification improves performance and is interesting in connection with x-ray emission spectrography (Chapters 7, 8, and 9). It consists in measuring the intensity of tin Ka relative to that of scattered x-rays entering the detector from an analyzing crystal set for the reflection of x-rays 2.2 A in wavelength. As the tin coating becomes thicker, increased attenuation of the x-rays scattered by the iron cause s the intensity ratio to increase more rapidly than does the intensity of tin Ka. Table 6-3 contains performance data for the Quantrol on Method II (modified). The instrument can also be set up to use industrially a modification of Method III. 

The extreme wavelength of the analytical lines of the light elements greatly reduces the number of satisfactory analyzing crystals. As... 

Fig. 3-8. Relationship between intensity of scattered x-rays and thickness of an aluminum-foil support. The x-ray tube was operated at 50 kv and 50 ma. A lithium fluoride analyzing crystal was used at 20 — 25°. (Authors unpublished results.)...

Analytical lines used, BaL l (2.567 A), CaKa (3.359 A), ZnKcx (1.436 A). Molybdenum target, helium path, rock salt analyzing crystal, and Geiger tube were used. The x-ray tube was operated at 50 kv, 30 ma (Zn) and 40 ma (Ba, Ca). 

Analysis, see also Absorptiometry X-ray emission spectrography look also under the respective materials of variance, 277, 283-288 Analyzing crystals, 115-124, 219, 220, 257, 260, 318-327... 

Analyzing crystals, resolution by, compared to pulse-height selection, 47, 61, 63... 

Edges, absorption, see Absorption edges EDT (EDDT) as analyzing crystal, 116-118, 220, 257, 260, 318-327 Effective wavelength of a polychromatic x-ray beam, determination, 8, 72, 76-78... 

Silica-alumina system, absorption and enhancement effects in x-ray emission spectrography, 222-224 Silicon, /as analyzing crystal, 318-327 determination by x-iay emission spectrography, 67, 219, 222-224, 260, 261, 329... 

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