Camera length

Sample B provided platinum crystallites that were analyzed by both EDS and MAED. MAED of several 3 nm crystallites shows a wide variation of orientations with respect to the electron beam, however, many of the patterns match (111) and (110) orientations. An example of the MAED patterns observed Is shown In Figure 2. The diffraction pattern was made with a 25 pm objective aperture at a camera length of 2 m. 

The Bright-Field symmetry is the symmetry of the transmitted disk (the central disk) of a Zone-Axis Pattern. It is observed on the same ZAP than the one used for the identification of the Whole-Pattern symmetry, but at a higher camera length and a shorter exposure time. Some examples are given on figure 3. The first one (Figure 3a) is the central disk of the Whole Pattern... 

Depending on purposes, a plastic film under the vapor-deposited C is dissolved away with a solvent. By this method, a very thin C support-film of smaller than lOnm in thickness can be made easily. An aluminum (Al) support-film can be made similarly, by vapor-deposition of Al onto a plastic film put on a grid and then by dissolving away the plastic film. The reflection rings from the Al support-film can be used as an internal reference to calibrate the camera length of SAED pattern, and this support film does give no amorphous halo. When an ultra-thin C support-film (less than 5nm in thickness) is desired, a microgrid (MG see Section 3.1.2) should be used on which an ultra-thin film made by indirect vapor-deposition of C has been put in advance. 

Where L is the experimental camera length (CL) and k is the electron wavelength determined by the electron accelerating voltage, O, in volts ... 

Figure 10.5 Schematic illustration showing the relation between camera length and recorded reciprocal space corresponding to a scattering angle.

As menhoned above, the unit cell of a crystalline specimen can be determined by SAED. However, the accuracy of the unit cell dimensions obtained is largely dependent upon the calibrahon of camera length, which is a funchon of specimen position and the conditions of the microscope. The procedure is complicated, and in most cases the unit cell parameters determined by SAED are less accurate than those obtained from XRD or neutron diffraction. Owing to the mulhple scattering problem, determination of space group by SAED is less reliable. Consequenhy, HRTEM is not an ideal technique for final determination of crystal structure. 

The three fixed wavelength stations described above include variable camera lengths, which allow access to a wide range of d spacings, (see Table 1). 

Figure 1. Transmission electron microscopy (TEM) images and selected area electron diffraction pattern (SAED) of preformed gold nanopaiticles before and after ultrasonic treatment A), C) and E) TEM images of gold nanopaiticles bef e soiication, after 20 rain and 45 min of ultrasonic treatment, respectively. B), D) and F) SAED patterns (camera length 360 nm) of gold nanopaiticles before ultrasonic treatment and after sonication for 20 min and 45 min respectively.

The wavelength of electrons (k) for 200 kV, which is used to obtain the pattern, should be 0.00251 nm according to Table 3.2. The diffraction photograph is taken at the camera length (L) of 1.0 m. Since the lattice parameter of NaCl (a) is 0.563 nm, we can find out that the Rm matches that of 200 and R matches that of 220, according Equation 3.18. Then, we should check whether the angle (RmRn) matches that between specific planes. The plane angle in a... 

Fig. 8.24. Evolution of the fractal dimension D of silica sol/gel samples with standard composition as a function of aging time. Data are obtained with two different camera lengths of the SAXS equipment in two different measurement runs. From de Lange et al. [43,44].

Figure 8. SAXS curves of a silica gel prepared at pH 3.9 from potassium water glass and hydrochloric acid a, freshly prepared silica gel recorded after 2 h of reaction b, same gel as in a, but after 1 year of aging at room temperature. The dotted line is a nonlinear least-squares fit of the fractal region in the curve and gives D = 2.0. The dashed line is from the Porod law (I < Q 4). In both a and b, two scattering curves measured at two different camera lengths (4.5 and 0.7 m) are combined to cover a broad scattering range (2 orders of magnitude in Q...

Fig. 3. Assembly of microtubule protein monitored by time-resolved X-ray scattering. The projection plot shows an experiment using the EMBL instrument X33, camera length 3 m, linear position-sensitive detector with 256 channels, 256 time frames of 3 sec per run (not all shown), temperature jumps from 3 to 37 °C and back (arrows). Note the increase in central scatter during assembly and the change in side maxima. The side maximum of the cold solution is due to rings, that of the warm solution is due to microtubules. From [11]...

The limit of diffuse scattering (L) — which corresponds to the SAXS-resolution — has been calculated for this type of optics for various camera length (Fig. 11 a). A comparison of the optimum in L (Lmax) with that of the polymer beamline at F1ASYLAB is shown in Fig, lib. At a comparable F2 9 m one obtains an increase in Lmax by a factor 15. The size of the beam at the sample is shown in Fig. 11c. 

Fig. 2. Intersection of the Ewald sphere with the reciprocal lattice showing the scattering angle for ZOLZ and HOLZ reflections in the case of a short camera length DP and schematic projection of a corresponding CBED pattern...

As final recommendations the specimen must be cooled in liquid N2 and several photographic plates in different conditions of apertures and camera length should be obtained. 

Different areas and slices to be explored are a function of the condenser aperture size and the demagnification of the upper objective polepiece. Camera length can be modified as is usual in any TEM instrument for obtaining the external rings. 

Figure 2.9 Bright-field TEM images ofthe PCBM/MDMO-PPV photoactive layer acquired at (a) 300 kV and (b) 80 kV acceleration voltage ADF-STEM images ofthe same sample acquired with camera lengths of (c) 100 mm...

Small-angle X-ray scattering (SAXS) studies were carried out using Daresbury Station 16.1 with the RAPID 2-dimensonal detector, with X-ray wavelength A= 141 pm and a camera length of 4 m. Scattering intensities were radially aver-... 

With SANS the camera length is fixed, but the pulsed time-of-flight system provides measurements in roughly the same colloidal range. 

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