An Analysis of Dissociation of Molecules in a High Resolution Electron Microscope

1973 ◽  
Vol 31 ◽  
pp. 486-487
Author(s):  
Mihir Parikh
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Cross Sections ◽  
Resolving Power ◽  
Peak Intensity ◽  
Molecular Film ◽  
Resolution Electron ◽  
Dissociation Cross Section ◽  
High Resolution Electron Microscope ◽  
The Stability

It is well known that the resolution of bio-molecules in a high resolution electron microscope depends not just on the physical resolving power of the instrument, but also on the stability of these molecules under the electron beam. Experimentally, the damage to the bio-molecules is commo ly monitored by the decrease in the intensity of the diffraction pattern, or more quantitatively by the decrease in the peaks of an energy loss spectrum. In the latter case the exposure, EC, to decrease the peak intensity from IO to I’O can be related to the molecular dissociation cross-section, σD, by EC = ℓn(IO /I’O) /ℓD. Qu ntitative data on damage cross-sections are just being reported, However, the microscopist needs to know the explicit dependence of damage on: (1) the molecular properties, (2) the density and characteristics of the molecular film and that of the support film, if any, (3) the temperature of the molecular film and (4) certain characteristics of the electron microscope used

Development of High Resolution Electron Microscope, JEM-100B

1968 ◽  
Vol 26 ◽  
pp. 298-299
Author(s):  
M. Watanabe ◽  
T. Yanaka ◽  
M. Yamamoto ◽  
S. Suzuki ◽  
Y. Nagahama ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Spherical Aberration ◽  
Point Of View ◽  
Resolving Power ◽  
Objective Lens ◽  
Stage Of Development ◽  
Resolution Electron ◽  
Microscopic Studies ◽  
High Resolution Electron Microscope ◽  
The Stability

The JEM-100B electron microscope has been developed with a view to the possibility of obtaining an ultimate resolving power at a beam accelerating voltage of 100kev. Prom the very nature of the instrument, the stability is fully ensured from a mechanical and electrical point of view. In the electron optical system, since highly excited lenses are utilized, image formation under the lowest aberration condition are ensured. The image forming system is of the 4-stage type which greatly expands the range of application not only in microscopic studies but also in the study of electron diffraction. Furthermore, with a view to simplifying instrument operation, various problems have been solved this enabling the instrument to be fully automated. The JEM-100B exhibits the following features.Objective Lens: At the present stage of development, fo=1.6mm. However, so as to be able to incorporate a lens (T. Yanaka et al, 1967) possessing an extremely small spherical aberration coefficient in the future, lens excitation has been made sufficiently high (8kA) and the movable aperture control knob and the specimen device have been designed accordingly.

Principles and performance of a 600 kV high resolution electron microscope

1980 ◽  
Vol 370 (1740) ◽  
pp. 1-16 ◽  
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Electron Gun ◽  
Resolving Power ◽  
Objective Lens ◽  
Optical Parameters ◽  
Resolution Electron ◽  
Pneumatic Suspension ◽  
High Resolution Electron Microscope ◽  
And Performance

The resolving power of the electron microscope as assessed by purely electron optical factors is of the order of 1 Å. The resolution obtainable in practice is limited by adventitious instabilities, mechanical and electrical in nature. The detailed design of a high resolution microscope follows from an analysis of these disturbances; its construction must be carried out with the highest precision. Special attention is paid to the electron gun, to the specimen stage and to the mounting of the microscope. For the Cambridge project, 600 kV has been adopted on the grounds of cost- effectiveness. It employs a lanthanum boride cathode and high stability electronics. A pneumatic suspension system supports the microscope when in operation, to isolate it from ambient vibrations. From the electron optical parameters of the condenser-objective lens, together with the recorded levels of residual disturbances, an image reso¬lution of 2.0 Å is predicted (at 600 kV), which should be improved to 1.5 Å by image processing. Initial results from thin specimens of minerals, metal particles and metallic glasses demonstrate that this performance is already closely approached.

Computer-Controlled Hrem Alignment Using Automated Diffractogram Analysis

1990 ◽  
Vol 48 (1) ◽  
pp. 532-533
Author(s):  
G.Y. Fan ◽  
O.L. Krivanek
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
The Other ◽  
Full Information ◽  
Resolution Electron ◽  
Skilled Operator ◽  
Automatic Alignment ◽  
High Resolution Electron Microscope ◽  
Computer Controlled ◽  
Recorded Image

Full alignment of a high resolution electron microscope (HREM) requires five parameters to be optimized: the illumination angle (beam tilt) x and y, defocus, and astigmatism magnitude and orientation. Because neither voltage nor current centering lead to the correct illumination angle, all the adjustments must be done on the basis of observing contrast changes in a recorded image. The full alignment can be carried out by a computer which is connected to a suitable image pick-up device and is able to control the microscope, sometimes with greater precision and speed than even a skilled operator can achieve. Two approaches to computer-controlled (automatic) alignment have been investigated. The first is based on measuring the dependence of the overall contrast in the image of a thin amorphous specimen on the relevant parameters, the other on measuring the image shift. Here we report on our progress in developing a new method, which makes use of the full information contained in a computed diffractogram.

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