Bragg maxima

Bragg maxima, 21 179-182 Brj-AIBrj catalyst, 37 172 Branched synthetic polymer, polyethylene m-ine, 29 215-220... 

At the lowest energies the ordinary Bragg maxima, which are so prominent at high energy, become poorly defined, and sometimes are... 

Fig. 9. Intensity-voltage plot (intensity versus A) of 00 beam from a clean W(112) surface (see Fig. 6d). Crystal rotated 5° around [01] axis so that specular beam could be measured (incidence brought 5" closer to [llT] surface direction). The experiment was performed in a post-acceleration tuhe and intensity on screen monitored hy telescopic photometer [data of Chang, (203, pp. 24—25)]. Heavy arrows show theoretical positions Fmax of Bragg maxima of order n calculated according to nX = n( 150.4/ Umax) = 2Uo(6) cos 5 . Identifiable Bragg maxima stand out clearly in the higher voltage range and are displaced by an inner potential of about 19 V. At lower voltage, the curve is complicated and is not well understood.

In a very strong standing light wave, an initially broad electron wave packet will be split into two parts, each being the envelope of many Bragg maxima, with the angle 20 between the split beams given by... 

As mentioned above, a special feature of the HBA/HNA system is that the monomer lengths are in the approximate ratio 3 4 and, as a result of this, the peak at c(-2.lX scarcely moves with polymer composition. This peak may therefore be considered as a Bragg maximum the point model can be thought of as a lattice repeating... 

In thin cells there is an additional effect of the interference from the parallel boundaries resulting in the spectral oscillations observed on both sides of the Bragg maximum. Such fringes are well seen in Fig. 12.7, the corresponding numerical calculations being made for the cholesteric slab of thickness 4 pm. Of course, in this case, the theory is more difficult [3]. 

A series of powder photographs was taken in a Norelco camera 360 mm. in circumference which holds the film in the Straumanis arrangement and permits a maximum Bragg angle of 87-6°. The copper K radiation was filtered through 0-001 in. nickel foil. Eastman No-Screen X-ray film was used throughout. All photographs were taken at room temperature, 26 + 2° C. 

Figure 4.4. X-rays scattered by atoms in an ordered lattice interfere constructively in directions given by Bragg s law. The angles of maximum intensity enable one to calculate the spacings between the lattice planes and allow furthermore for phase identification. Diffractograms are measured as a function of the angle 26. When the sample is a...

After a simple Fourier inversion of a set of magnetic structure factors MbU, one can retrieve the magnetisation density. A much better result, e.g. the most probable density map, can be obtained using the Maximum Entropy (MaxEnt) method. It takes into account the lack and the uncertainty of the information not all the Bragg reflections are accessible on the instrument, and all the values contained in the error bars are satisfactory and have to be considered. However, as this method extracts all the information contained in the data, it is important to keep in mind that it may show spurious small details associated to a low accuracy and/or a specific lack of information located in (/-space. 

For high order reflections with a large g, the rapid increase in the excitation error away from the Bragg condition results a rapid decrease in diffraction intensity. Under the kinematical condition, the maximum intensity occurs at the Bragg condition, which appears as a straight line within a small convergence angle. 

Use the tilt adjustment on the analyser to maximise the intensity in the Bragg peak. This must be done iteratively, tilting and relocating the Bragg peak. When the maximum has been reached, the analyser is correctly set... 

Plaee the speeimen on the seeond axis and with the deteetor axis rotated to twiee the speeimen Bragg angle, loeate the Bragg peak of the speeimen as in a double-axis experiment. Perform any necessary tilt adjustments of the specimen exactly as for double-axis diffractioa (If you wish you may perform a double-axis experiment at this stage.) Set everything onto the maximum of the Bragg peak. 

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