Wavelength spread

We therefore need to limit the divergence and wavelength spread of the beam incident upon the specimen. Beam conditioners are used to collimate and to... 

Figure 2.4 shows the elements of a high resolution diffractometer. The beam conditioner controls the divergence and wavelength spread of the beam by a combination of diffracting elements and angular-limiting apertures. The latter may also control the spatial width of the beam. This falls upon a specimen,... 

All the above techniques use incident monochromatic radiation, usually focus in one or two dimensions. However for cases a) and d) the reduction of radiation damage and more particularly in kinetic crystallography the use of polychromatic data collection is yielding promising results. This technique makes combined use of the intensity and collimation of the SR beam with a large wavelength spread for Laue data colla tion from protein single crystals. 

The wavelength used does not, in general, affect to any serious extent the relative intensities of the various arcs in a pattern, but it doep control the scale of the pattern the longer wavelengths spread out the pattern, while the shorter wavelengths contract it. 

The main drawbacks to the use of solar energy are its rather low density (ca. 1 kW m-2 on i clear day with the sun directly overhead), its wide wavelength spread and its somewhat unpredict able nature caused by different weather patterns. Nevertheless, calculations have shown that it i in theory possible to provide the energy needs of the whole world provided that the energy cai... 

All of the other phenomena associated with waves can also be observed in particles. For example, in 1927 Davisson and Germer accelerated a beam of electrons to a known kinetic energy and showed that these electrons could be diffracted off a nickel crystal, just as X-rays are diffracted (see Figure 3.8). Just as with photons, interference is not always seen if the wavelength spread or the slits are large, the fringes wash out. This also explains why interference is not seen with macroscopic objects, such as buckshot—the wavelength is far too small. 

The Bronsted acid/base pair pyridinium/pyridine is unusual because redox potentials are available for both partners in an accessible range [35]. This allows detailed anticipation of the sensory behaviour of systems containing pyridine receptors. (49), whose fluorescence properties have received some attention before [113], is a member of a family of PET sensors for protons whose excitation and emission wavelengths spread over a substantial fraction of the accessible optical spectrum without compromising sensory action [114]. 

Historically, all the early neutron sources were of the conventional reactor type, and a large monochromating crystal was commonly employed (for single-crystal diffraction experiments) to select neutrons with a small wavelength spread in order to produce a monochromatic neutron beam. The rest... 

Consider now the wide angle scattering resolution. According to Rosenbaum and Holmes the width of a diffraction spot is determined by the demagnified source size — a —, the intrinsic width of a reflection and a dispersion term to account for the wavelength spread ... 

There are many geometrical contributions to the angular resolution (c.g., angular width of the receiving slit in front of the detector). Another contribution comes from finite wavelength spread of the incident beam A2. From Equation (40) we get the angular dispersion to be ... 

Figure 1.14 Angular dependence of the intrinsic peak width (resolution function) of the diffractometer due to the wavelength spread between Cu Kai and Cu Ka2 (about 12eV).

The second optical element is a triangular Ge (111) monochromator with an oblique cut of 10.5° placed approximately 10 m from the mirror. The monochromator can be bent to provide a vertical demagnification of the source of approximately 10 1 in the horizontal direction at the camera. The wavelength used in the experiments described below was usually 1.488 A or 1.608 A. The wavelength spread, AX/X, was typically 10-3. The arrangement on the wiggler station is similar. 

Fig. 32. Typical experimental data ( + ) for an isometric protein-RNA plant virus, southern bean mosaic virus (SBMV) in its (a) compact and (b) swollen states [555]. For a given H20 buffer content, note the shift in the position of the subsidiary mimima to lower Q which accompanies the increase in the virus radius of about 10% in the swollen state. The continuous curve at each contrast is that calculated for a four-shell model of SBMV, and has been smeared to allow for neutron beam divergence and wavelength spread.

Following Pedersen [78], there are three main contributions that have to be incorporated when a typical diffractometer with a pin-hole geometry is used wavelength spread, coUimation effects, and the detector resolution. Using a Gaussian function for each effect, the resolution function is given by ... 

As discussed earlier, for K 1 only one spectral harmonic is emitted, at X=Xw/2K2(Fig.8) its wavelength is independent of Bq and the power emitted is proportional to the wavelength spread is small if the radiation is observed through a pinhole on the axis of the undulator (Fig.Sa). Fig.Sc illustrates that the spectrum includes many harmonics when K>1 under certain conditions, their envelope ressemblesa normal synchrotron radiation spectrum (fig.8d). 

Linewidth Frequency or wavelength spread over which emission, absorption, and gain occur in the laser amplifier. 

Figure 7. Double-crystal arrangements. In the parallel (+, -) setting, where both lattice spacings of the first and the second crystal parts are equal, all the wavelengths components from the first crystal are diffracted by the second crystal as well. When the lattice spacing of the first is different from the second crystal, it is called the nonparallel (+, -) setting. The scheme as shown in the bottom is called the (+, +) setting. In the nonparallel (+, -) and the (+, +) setting only small angular and wavelength spreads can be diffracted by the second crystal. (From Ref. 22.)...

E. Resolution. The Bragg law was derived under ideal conditions (the use of a monochromatic, perfectly parallel beam and of a perfect crystal). In practice, the diffracted beam has a wavelength spread that depends on the divergence of the incident beam (this beam is not monochromatic) and the mosaic spread of the crystal. (The mosaic spread is taken up in Section F below.)... 

What determines the wavelength spread 6X of the diffracted beam ... 

This is the explanation for the observation that the intermediate scattering functions which are typical for simple polymer systems do not suffer from significant distortions due to the typical large incoming neutton wavelength spread. 

Figure Al Symmetry scan showing the echo signal as obtained with a wavelength spread of 10% FWHM. The symmetry point is at about 1A phase current. The dash-dotted lines indicate the intensity limits low (/down) forthe blocking combination of analyzer and ir-flipper, high (/ p) forthe transmitting combination. The echo amplitude may be obtained by nonlinear fitting for an arbitrary number of points or close to the symmetry point by direct calculation from 3 (minimum) or 4 points (red diamonds) with fixed known phase angle step (here 90°).

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