Possible applications of fraunhofer holography in high resolution electron microscopy

1978 ◽  
Vol 36 (1) ◽  
pp. 222-223 ◽  
Author(s):  
N. Bonnet ◽  
M. Troyon ◽  
P. Gallion
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Transfer Function ◽  
Radiation Damage ◽  
High Resolution Electron Microscopy ◽  
Far Field ◽  
Field Region ◽  
Crystalline Materials ◽  
Resolution Electron ◽  
The Ideal

Two main problems in high resolution electron microscopy are first, the existence of gaps in the transfer function, and then the difficulty to find complex amplitude of the diffracted wawe from registered intensity. The solution of this second problem is in most cases only intended by the realization of several micrographs in different conditions (defocusing distance, illuminating angle, complementary objective apertures…) which can lead to severe problems of contamination or radiation damage for certain specimens.Fraunhofer holography can in principle solve both problems stated above (1,2). The microscope objective is strongly defocused (far-field region) so that the two diffracted beams do not interfere. The ideal transfer function after reconstruction is then unity and the twin image do not overlap on the reconstructed one.We show some applications of the method and results of preliminary tests.Possible application to the study of cavitiesSmall voids (or gas-filled bubbles) created by irradiation in crystalline materials can be observed near the Scherzer focus, but it is then difficult to extract other informations than the approximated size.

scholarly journals Atomic Matching Across Internal Interfaces

1989 ◽  
Vol 153 ◽  
Author(s):  
Karl L. Merkle
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Large Fraction ◽  
High Resolution Electron Microscopy ◽  
Low Energy ◽  
Ideal Lattice ◽  
Interatomic Distances ◽  
Resolution Electron ◽  
Atomic Coordination ◽  
The Ideal

AbstractThe atomic structure of internal interfaces in dense-packed systems has been investigated by high-resolution electron microscopy (HREM). Similarities between the atomic relaxations in heterophase Interfaces and certain largeangle grain boundaries have been observed. In both types of interfaces localization of misfit leads to regions of good atomic matching within the interface separated by misfit dislocation-like defects. It appears that, whenever possible, the GB structures assume configurations in which the atomic coordination is not too much different from the ideal lattice. It is suggested that these kinds of relaxations primarily occur whenever the translational periods along the GB are large or when the interatomic distances are incommensurate. Incorporation of low index planes into the GB appears to lead to preferred, i.e. low energy structures, that can be quite dense with good atomic matching across a large fraction of the interface.

High-resolution electron microscopy of beam-sensitive specimens: Results with paraffin

1986 ◽  
Vol 44 ◽  
pp. 10-13
Author(s):  
F. Zemlin ◽  
E. Reuber ◽  
E. Beckmann ◽  
D. Dorset
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Radiation Damage ◽  
High Resolution Electron Microscopy ◽  
Objective Lens ◽  
Resolution Electron ◽  
Electron Microscopical

Many of the most interesting specimens are so severely damaged during the electron microscopical imaging that no useful image emerges from the electron noise. One method of reducing this radiation damage is to cool the specimen, and if this helps it seems reasonable to cool it down as far as possible. This goal is reached most straightforwardly by using the Siemens helium-cooled superconducting objective lens designed by I. Dietrich and co-workers.

High resolution electron microscopy of molecular crystals III. Radiation processes at room temperature

1984 ◽  
Vol 393 (1805) ◽  
pp. 353-369 ◽  
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Radiation Damage ◽  
Room Temperature ◽  
High Resolution Electron Microscopy ◽  
Resolution Electron ◽  
Wide Range ◽  
Preferential Loss ◽  
Peripheral Atom ◽  
Radiation Processes

High resolution electron microscopy has shown that the morphology of radiation damage was similar for a wide range of crystalline organic compounds. The considerable lack of contrast suffered by halogenated compounds in regions of radiation damage seems to arise from preferential loss of halogen from these areas. This aspect of loss of peripheral atom from the molecule is also supported by results obtained by encapsulating the specimen between carbon and other films. The encapsulation reduced the effect of radiation damage and it is suggested that the encapsulation held the peripheral atoms in the crystal, which enabled them to recombine with ions and radicals formed by the damage and to prevent molecular degradation. A reaction mechanism based on this premise is proposed.

Structural analysis of the surface-layer protein of spirillum serpens by high-resolution electron microscopy

1983 ◽  
Vol 41 ◽  
pp. 738-739
Author(s):  
W. H. Wu ◽  
R. M. Glaeser
Keyword(s):  
Electron Microscopy ◽  
Surface Layer ◽  
Structural Analysis ◽  
High Resolution ◽  
Low Dose ◽  
High Resolution Electron Microscopy ◽  
Optical Diffraction ◽  
Surface Layer Protein ◽  
Morphological Unit ◽  
Resolution Electron

Spirillum serpens possesses a surface layer protein which exhibits a regular hexagonal packing of the morphological subunits. A morphological model of the structure of the protein has been proposed at a resolution of about 25 Å, in which the morphological unit might be described as having the appearance of a flared-out, hollow cylinder with six ÅspokesÅ at the flared end. In order to understand the detailed association of the macromolecules, it is necessary to do a high resolution structural analysis. Large, single layered arrays of the surface layer protein have been obtained for this purpose by means of extensive heating in high CaCl2, a procedure derived from that of Buckmire and Murray. Low dose, low temperature electron microscopy has been applied to the large arrays.As a first step, the samples were negatively stained with neutralized phosphotungstic acid, and the specimens were imaged at 40,000 magnification by use of a high resolution cold stage on a JE0L 100B. Low dose images were recorded with exposures of 7-9 electrons/Å2. The micrographs obtained (Fig. 1) were examined by use of optical diffraction (Fig. 2) to tell what areas were especially well ordered.

Electron microscopy of rabbit FC crystals

1983 ◽  
Vol 41 ◽  
pp. 730-731
Author(s):  
Robert A. Grant ◽  
Laura L. Degn ◽  
Wah Chiu ◽  
John Robinson
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
High Resolution Electron Microscopy ◽  
Molecular Replacement ◽  
X Ray ◽  
X Ray Crystallography ◽  
Resolution Electron ◽  
Replacement Technique ◽  
Hydrated Crystal ◽  
Molecular Structure Analysis

Proteolytic digestion of the immunoglobulin IgG with papain cleaves the molecule into an antigen binding fragment, Fab, and a compliment binding fragment, Fc. Structures of intact immunoglobulin, Fab and Fc from various sources have been solved by X-ray crystallography. Rabbit Fc can be crystallized as thin platelets suitable for high resolution electron microscopy. The structure of rabbit Fc can be expected to be similar to the known structure of human Fc, making it an ideal specimen for comparing the X-ray and electron crystallographic techniques and for the application of the molecular replacement technique to electron crystallography. Thin protein crystals embedded in ice diffract to high resolution. A low resolution image of a frozen, hydrated crystal can be expected to have a better contrast than a glucose embedded crystal due to the larger density difference between protein and ice compared to protein and glucose. For these reasons we are using an ice embedding technique to prepare the rabbit Fc crystals for molecular structure analysis by electron microscopy.

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