Investigation of low-loss spectra and near-edge fine structure of polymers by peels

1996 ◽  
Vol 54 ◽  
pp. 158-159
Author(s):  
W. Heckmann
Keyword(s):  
Electron Microscopy ◽  
High Sensitivity ◽  
High Energy ◽  
High Energy Resolution ◽  
Imaging Method ◽  
Low Loss ◽  
Transmission Electron ◽  
Electron Microscopes ◽  
Electron Energy Loss ◽  
Loss Range

Transmission electron microscopy has changed from a purely imaging method to an analytical method. This has been facilitated particularly by equipping electron microscopes with energy filters and with parallel electron energy loss spectrometers (PEELS). Because of their relatively high energy resolution (1 to 2 eV) they provide information not only on the elements present but also on the type of bonds between the molecular groups. Polymers are radiation sensitive and the molecular bonds change as the spectrum is being recorded. This can be observed with PEEL spectrometers that are able to record spectra with high sensitivity and in rapid succession.A PEEL spectrum can be divided into a low loss range and an inner shell loss range of higher energy. The low loss spectra of polymers always show a broad peak at about 22 eV and a further peak at 7 eV, if aromatic groups are present, as is the case with PS (Fig. 1). In the course of exposure, the intensity of this peak decreases, a sign that the benzene ring is destroyed by the radiation (Fig. 2).

Computer-Controlled Transmission Electron Microscopy: Automated Tomography

2001 ◽  
Vol 7 (S2) ◽  
pp. 968-969
Author(s):  
Theo van der Krift ◽  
Ulrike Ziese ◽  
Willie Geerts ◽  
Bram Koster
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
User Interfaces ◽  
Electron Tomography ◽  
Imaging Method ◽  
Optical Elements ◽  
Computer Screen ◽  
Transmission Electron ◽  
Computer Controlled ◽  
Electron Microscopes

The integration of computers and transmission electron microscopes (TEM) in combination with the availability of computer networks evolves in various fields of computer-controlled electron microscopy. Three layers can be discriminated: control of electron-optical elements in the column, automation of specific microscope operation procedures and display of user interfaces. The first layer of development concerns the computer-control of the optical elements of the transmission electron microscope (TEM). Most of the TEM manufacturers have transformed their optical instruments into computer-controlled image capturing devices. Nowadays, the required controls for the currents through lenses and coils of the optical column can be accessed by computer software. The second layer of development is aimed toward further automation of instrument operation. For specific microscope applications, dedicated automated microscope-control procedures are carried out. in this paper, we will discuss our ongoing efforts on this second level towards fully automated electron tomography. The third layer of development concerns virtual- or telemicroscopy. Most telemicroscopy applications duplicate the computer-screen (with accessory controls) at the microscope-site to a computer-screen at another site. This approach allows sharing of equipment, monitoring of instruments by supervisors, as well as collaboration between experts at remote locations.Electron tomography is a three-dimensional (3D) imaging method with transmission electron microscopy (TEM) that provides high-resolution 3D images of structural arrangements. with electron tomography a series of images is acquired of a sample that is tilted over a large angular range (±70°) with small angular tilt increments.

A Wien Filter Electron Energy Loss Spectrometer for Transmission Electron Microscopy

1990 ◽  
Vol 48 (2) ◽  
pp. 32-33
Author(s):  
K. Tsuno ◽  
J. Ohyama ◽  
M. Kato ◽  
J. Kimura ◽  
M. Kai ◽  
...  
Keyword(s):  
Imaging System ◽  
Optical Axis ◽  
Detection System ◽  
High Energy ◽  
High Energy Resolution ◽  
Wien Filter ◽  
Magnetic Forces ◽  
Transmission Electron ◽  
Electron Energy Loss ◽  
Post Filter

A retarding Wien filter has been installed in the transmission electron microscope (TEM) JEM-1200EX. The filter is immersed in a high potential (-Ht + Uo ) nearly equal to the accelerating potential (-Ht) to get high energy resolution. The Wien filter consists of crossed electric (E) and magnetic (B) fields perpendicular to the optical axis. Electrons with a particular velocity v have a straight optical axis if the balancing condition between electric and magnetic forces (Wien condition: E=vB) is satisfied. Electrons with different velocity are deflected.Fig. 1 shows a schematic outline of the present instrument. It consists of (1) TEM, (2) an analyzer made of the Wien filter, deflectors and post filter lenses, and (3) a TV camera imaging system and serial detection system. The analyzer and a serial detection system are controlled by a personal computer PC-9801VX (PC). Table 1 shows currents and voltages of the filter, lenses and deflectors (upper) and those for TEM (lower).

Elektronen-Energie-Verlust-Spektroskopische Untersuchungen an Luftfiltern zur Bewertung der Luftqualität / Electron-Energy-Loss-Spectroscopical Investigations on Air Filters for the Analysis of the Air Quality

1988 ◽  
Vol 43 (3-4) ◽  
pp. 155-161 ◽  
Author(s):  
Bernhard Wolf
Keyword(s):  
Air Quality ◽  
Energy Loss ◽  
Electron Energy ◽  
High Sensitivity ◽  
High Energy ◽  
High Energy Resolution ◽  
X Ray ◽  
Simple Arrangement ◽  
Wet Chemical ◽  
Electron Energy Loss

In trace analysis it is more and more attempted to replace wet-chemical detection procedures by methods which allow a quantitative analysis without any material disintegration, but on exploiting the characteristic physical properties of the components searched for. Based on a procedure for physical and biological valuation of the air quality by means of X-ray microanalysis (WDX/EDX), a procedure which was previously developed by our group, we deepened our investigations by the help of electron-energy-loss-spectroscopy (EELS). The combination of that procedure with EELS proved to be very advantageous as it revealed a high sensitivity as well as a high energy resolution. The main advantages are to be found in the simple arrangement of the sample detector and in the fact, not only being able to examine deposits microscopically, but also to analyze them chemically without disintegrating the material. Thus loss of material and denaturation are largely excluded.

Localization of Green Fluorescent Protein Absorbance by Energy Filtered Transmission Electron Microscopy

2000 ◽  
Vol 6 (S2) ◽  
pp. 324-325
Author(s):  
J. A. Davis ◽  
R. G. Garces ◽  
J.-Y. Diao ◽  
F. P. Ottensmeyer
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Green Fluorescent Protein ◽  
Energy Loss ◽  
Energy Resolution ◽  
Fluorescent Protein ◽  
High Energy ◽  
High Energy Resolution ◽  
Transmission Electron ◽  
Green Fluorescent

Energy filtered transmission electron microscopy has the potential to provide high resolution, spatially resolved, atomic and chemical information. However, aberrations generated by the electron spectrometer blur the energy resolution and limit the atomic or molecular distributions that can be studied. Energy absorptions corresponding to the visible light range fall below an energy loss of 5 eV. The selection of electrons that have lost an amount of energy corresponding to chromophore absorption by the sample thus requires a spectrometer with a high energy resolution over the full image plane. A corrected prism-mirror-prism filter that has a resolution of 1.1 eV, sufficient to select these low energy loss electrons, was developed and installed by us in a Zeiss EM902. Its imaging capability was verified for a number of different chromophores. The chromophore currently under study is that of the green fluorescent protein (GFP).

High-energy-resolution monochromator for aberration-corrected scanning transmission electron microscopy/electron energy-loss spectroscopy

2009 ◽  
Vol 367 (1903) ◽  
pp. 3683-3697 ◽  
Author(s):  
Ondrej L. Krivanek ◽  
Jonathan P. Ursin ◽  
Neil J. Bacon ◽  
George J. Corbin ◽  
Niklas Dellby ◽  
...  
Keyword(s):  
Energy Loss ◽  
Electron Energy ◽  
Energy Resolution ◽  
Electron Energy Loss Spectroscopy ◽  
High Energy ◽  
High Energy Resolution ◽  
Scanning Transmission Electron ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Electron Energy Loss

An all-magnetic monochromator/spectrometer system for sub-30 meV energy-resolution electron energy-loss spectroscopy in the scanning transmission electron microscope is described. It will link the energy being selected by the monochromator to the energy being analysed by the spectrometer, without resorting to decelerating the electron beam. This will allow it to attain spectral energy stability comparable to systems using monochromators and spectrometers that are raised to near the high voltage of the instrument. It will also be able to correct the chromatic aberration of the probe-forming column. It should be able to provide variable energy resolution down to approximately 10 meV and spatial resolution less than 1 Å.

A new method for determining sample thickness: A comparison to experimental results

1993 ◽  
Vol 51 ◽  
pp. 582-583
Author(s):  
John Blackson ◽  
Suichu Luo ◽  
David C Joy
Keyword(s):  
Electron Microscopy ◽  
Measurement Errors ◽  
Theoretical Method ◽  
Sample Thickness ◽  
Low Loss ◽  
Quantitative Electron Microscopy ◽  
Transmission Electron ◽  
Chromium Films ◽  
Electron Energy Loss ◽  
Diamond Knife

Sample thickness is an important parameter in quantitative electron microscopy,. Several methods for determining sample thickness have been described previously. A theoretical method presented here utilizes the low loss region of the electron energy loss spectrum to calculate sample thickness. The method avoids many of the limitations of other methods and is applicable to a wide variety of samples. The method is compared to film thicknesses determined experimentally as described below.Chromium films were deposited simultaneously onto collodion supported TEM grids and cured epoxy blanks using a Denton Hi Res 100 coater equipped with a Syton quartz crystal monitor. The cured epoxy blanks were covered with a layer of unpolymerized epoxy that was then cured. The chromium sandwich was cross sectioned using ultramicrotomy techniques employing a diamond knife. Sections were produced which were as thin as possible (<50 nm) to minimize measurement errors. Chromium film thickness was determined directly using transmission electron microscopy (Fig. 1).

Energy-Filtered Electron Microscopy (EFEM) of Frozen Hydrated Biological Specimens

1990 ◽  
Vol 48 (1) ◽  
pp. 274-275
Author(s):  
Wolfgang Probst ◽  
Erhard Zellmann ◽  
Richard Bauer
Keyword(s):  
Core Loss ◽  
Low Loss ◽  
Transmission Electron ◽  
Freeze Dried ◽  
Before And After ◽  
Electron Microscopes ◽  
Blurred Images ◽  
Physical Reasons ◽  
Loss Range ◽  
Great Stride

The preparation of hydrated biological specimens for the use in a TEM has made a great stride foreward due to the work of Dubochet et al. on vitrification and Muller et al. on high pressure freezing. Transfer units and cryo stages for the microscopes allow imaging of specimens in the 100K range. Due to simple physical reasons, however, contrast of such kinds of specimen is still a problemm in conventional transmission electron microscopes (CTEM). Solutions as they are provided by an EFEM will be shown and explained in the following.Ice is the main constituent of frozen hydrated specimens. The large ratio of inelastic-to-elastic total cross section of 4.0 in case of ice which is even more than that for carbon results in an unavoidable high amount of inelastically scattered electrons. Blurred images and lacking contrast are due to that fact. The EEL spectra from a frozen hydrated section of biological material before and after freeze drying in the microscope document this fact. (Figure 1). Increased scattering probability and thickness contribute to the inelastic loss. In Figure 2 the EEL spectrum from a thin pure ice layer without any support is compared to the spectrum from thin freeze dried cryo section on a thin support. In case of ice the maximum of the low loss range is clearly shifted towards zero loss, mainly due to oxygen low loss and plasmon and to hydrogen core loss. Thus for the images shown in the following Figures a narrow energy window of 10 eV is used really to cut off all the inelastically scattered electrons.

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