Energy Loss Imaging in Biology

1982 ◽  
Vol 40 ◽  
pp. 416-419
Author(s):  
H. Shuman ◽  
A.V. Somlyo ◽  
A.P. Somlyo ◽  
T. Frey ◽  
D. Safer
Keyword(s):  
Electron Microscope ◽  
Energy Loss ◽  
Cross Section ◽  
Cross Sections ◽  
Count Rate ◽  
Electron Flux ◽  
Characteristic Energy ◽  
Spectrometer Slit ◽  
Electron Energy Loss ◽  
Sensitive Method

It has been recognized for sometime that electron energy loss spectroscopy (EELS) is potentially the most sensitive method of measuring elemental composition in the electron microscope. Magnetic sector spectrometers currently in use collect most of the inelastically scattered electrons, while the cross sections for ionization of the L2 3 levels of the biologically important elements are large. The energies of the theoretically predicted L2 3 absorption edge maxima and their corresponding differential cross section for lOmrad collection and 80keV incident electrons are shown in Table I. The characteristic energy loss electron count rate expected from one atom with lOeV spectrometer slit width and lOOA/cm2 (the maximum available from a tungsten hairpin) electron flux at the specimen, indicates that the minimum detectable mass sensitivity of EELS will be high. An experimentally determined count rate and cross section for the Fe M2, 3 edge was determined from the ferritin images shown in Fig. 1.

Convenient multi-channel averaging for electron energy loss spectroscopy in the STEM

1978 ◽  
Vol 36 (1) ◽  
pp. 532-533
Author(s):  
P.E. Batson ◽  
J.N. Chapman ◽  
A.J. Craven ◽  
R.P. Ferrier
Keyword(s):  
Fine Structure ◽  
Energy Loss ◽  
Electron Energy ◽  
Cross Sections ◽  
Electron Energy Loss Spectroscopy ◽  
Cavendish Laboratory ◽  
Characteristic Energy ◽  
Additional Information ◽  
Ultimate Sensitivity ◽  
Electron Energy Loss

Electron energy loss spectroscopy (EELS) of electrons which have produced excitation of atomic electron core states promises to provide a powerful microanalytical tool. To assess fully the range of applications of the technique and its ultimate sensitivity in any given circumstance,accurate cross-sections differential in energy and scattering angle are required for both the characteristic energy loss electrons and for those loss electrons which contribute a background. In addition there is the possibility of gaining additional information on the nature of the specimen from the fine structure at the energy loss edge (Isaacson and Johnson 1975) and from the extended fine structure (EXELFS) beyond the edge (Colliex et al 1976), although neither of these phenomena are as yet well understood.We are currently investigating a number of aspects of EELS using a Vacuum Generators HB5 FEGSTEM at the Cavendish Laboratory, Cambridge. This is fitted with a magnetic spectrometer with air cored magnetic deflection at the magnet exit which can provide rapid energy scans without hysteresis.

A simple parameterization scheme for inner-shell cross sections

1988 ◽  
Vol 46 ◽  
pp. 532-533
Author(s):  
R.F. Egerton
Keyword(s):  
Solid State ◽  
Energy Loss ◽  
Cross Section ◽  
Cross Sections ◽  
Elemental Analysis ◽  
Incident Energy ◽  
Core Loss ◽  
Dipole Oscillator ◽  
Electron Energy Loss ◽  
Hand Calculator

Quantitative elemental analysis by electron energy-loss spectroscopy requires values of core-loss cross section σ(β,Δ) integrated up to a scattering angle β and over an energy range Δ above the ionization threshold. Such cross sections can be calculated using atomic models [1-3], neglecting solid-state effects. They can also be determined experimentally [4,5], but only for particular values of β,Δ and incident energy E0. By representing σ(β,Δ) in terms of an integrated dipole oscillator strength f(Δ) which is independent of β and E0, we realize two advantages: (1) measurements on solids can be directly compared with one another and with theory, and (2) values of σ(β,Δ) for K, L and M edges can be derived from tabulated values of f(Δ) by use of a hand calculator or a very short computer program.

Data Acquisition and Handling Unit for a Quantitative Use of Electron Energy Loss Spectroscopy

1977 ◽  
Vol 35 ◽  
pp. 232-233 ◽  
Author(s):  
P. Trebbia ◽  
P. Ballongue ◽  
C. Colliex
Keyword(s):  
Electron Microscope ◽  
Energy Loss ◽  
Electron Energy ◽  
Electron Energy Loss Spectroscopy ◽  
Single Channel ◽  
Detection System ◽  
Surface Barrier ◽  
Solid State Detector ◽  
Electrostatic Mirror ◽  
Electron Energy Loss

An effective use of electron energy loss spectroscopy for chemical characterization of selected areas in the electron microscope can only be achieved with the development of quantitative measurements capabilities.The experimental assembly, which is sketched in Fig.l, has therefore been carried out. It comprises four main elements.The analytical transmission electron microscope is a conventional microscope fitted with a Castaing and Henry dispersive unit (magnetic prism and electrostatic mirror). Recent modifications include the improvement of the vacuum in the specimen chamber (below 10-6 torr) and the adaptation of a new electrostatic mirror.The detection system, similar to the one described by Hermann et al (1), is located in a separate chamber below the fluorescent screen which visualizes the energy loss spectrum. Variable apertures select the electrons, which have lost an energy AE within an energy window smaller than 1 eV, in front of a surface barrier solid state detector RTC BPY 52 100 S.Q. The saw tooth signal delivered by a charge sensitive preamplifier (decay time of 5.10-5 S) is amplified, shaped into a gaussian profile through an active filter and counted by a single channel analyser.

Oxygen K near edge structures studied with multiple scattering calculations

1988 ◽  
Vol 46 ◽  
pp. 504-505
Author(s):  
Xudong Weng ◽  
Peter Rez
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Partial Cross Section ◽  
Energy Window ◽  
Edge Structure ◽  
Fine Structures ◽  
Hydrogenic Model ◽  
Electron Energy Loss ◽  
Quantitative Chemical

In electron energy loss spectroscopy, quantitative chemical microanalysis is performed by comparison of the intensity under a specific inner shell edge with the corresponding partial cross section. There are two commonly used models for calculations of atomic partial cross sections, the hydrogenic model and the Hartree-Slater model. Partial cross sections could also be measured from standards of known compositions. These partial cross sections are complicated by variations in the edge shapes, such as the near edge structure (ELNES) and extended fine structures (ELEXFS). The role of these solid state effects in the partial cross sections, and the transferability of the partial cross sections from material to material, has yet to be fully explored. In this work, we consider the oxygen K edge in several oxides as oxygen is present in many materials. Since the energy window of interest is in the range of 20-100 eV, we limit ourselves to the near edge structures.

Background Fitting in the Low-Loss Region of Electron Energy Loss Spectra

1990 ◽  
Vol 48 (2) ◽  
pp. 56-57
Author(s):  
C P Scott ◽  
A J Craven ◽  
C J Gilmore ◽  
A W Bowen
Keyword(s):  
Energy Loss ◽  
Multiple Scattering ◽  
Simple Form ◽  
Single Scattering ◽  
Low Loss ◽  
Characteristic Energy ◽  
Normal Method ◽  
Fitting In ◽  
Electron Energy Loss ◽  
Electron Energy Loss Spectra

The normal method of background subtraction in quantitative EELS analysis involves fitting an expression of the form I=AE-r to an energy window preceding the edge of interest; E is energy loss, A and r are fitting parameters. The calculated fit is then extrapolated under the edge, allowing the required signal to be extracted. In the case where the characteristic energy loss is small (E < 100eV), the background does not approximate to this simple form. One cause of this is multiple scattering. Even if the effects of multiple scattering are removed by deconvolution, it is not clear that the background from the recovered single scattering distribution follows this simple form, and, in any case, deconvolution can introduce artefacts.The above difficulties are particularly severe in the case of Al-Li alloys, where the Li K edge at ~52eV overlaps the Al L2,3 edge at ~72eV, and sharp plasmon peaks occur at intervals of ~15eV in the low loss region. An alternative background fitting technique, based on the work of Zanchi et al, has been tested on spectra taken from pure Al films, with a view to extending the analysis to Al-Li alloys.

A Poor Man’s Approach to Semi-Quantitative Analysis with Electron Energy Loss Spectroscopy

1980 ◽  
Vol 38 ◽  
pp. 110-111
Author(s):  
M. Isaacson
Keyword(s):  
Quantitative Analysis ◽  
Energy Loss ◽  
Electron Energy ◽  
Cross Section ◽  
Electron Energy Loss Spectroscopy ◽  
Excitation Cross Section ◽  
Incident Electron ◽  
Integral Cross Section ◽  
Image Position ◽  
Electron Energy Loss

In an earlier paper1 it was found that to a good approximation, the efficiency of collection of electrons that had lost energy due to an inner shell excitation could be written as where σE was the total excitation cross-section and σE(θ, Δ) was the integral cross-section for scattering within an angle θ and with an energy loss up to an energy Δ from the excitation edge, EE. We then obtained: where , with P being the momentum of the incident electron of velocity v. The parameter r was due to the assumption that d2σ/dEdΩ∞E−r for energy loss E. In reference 1 it was assumed that r was a constant.

Information and Dose in the Scanning Transmission Ion Microscope

1980 ◽  
Vol 38 ◽  
pp. 232-233
Author(s):  
Fox T. R. ◽  
R. Levi-Setti
Keyword(s):  
Information Retrieval ◽  
Electron Microscope ◽  
Elastic Scattering ◽  
Energy Loss ◽  
Cross Sections ◽  
Previous Analysis ◽  
Single Scattering ◽  
Screening Length ◽  
Relative Damage ◽  
Scanning Transmission

At an earlier meeting [1], we discussed information retrieval in the scanning transmission ion microscope (STIM) compared with the electron microscope at the same energy. We treated elastic scattering contrast, using total elastic cross sections; relative damage was estimated from energy loss data. This treatment is valid for “thin” specimens, where the incident particles suffer only single scattering. Since proton cross sections exceed electron cross sections, a given specimen (e.g., 1 μg/cm2 of carbon at 25 keV) may be thin for electrons but “thick” for protons. Therefore, we now extend our previous analysis to include multiple scattering. Our proton results are based on the calculations of Sigmund and Winterbon [2], for 25 keV protons on carbon, using a Thomas-Fermi screened potential with a screening length of 0.0226 nm. The electron results are from Crewe and Groves [3] at 30 keV.

scholarly journals First negative system of N<sub>2</sub><sup>+</sup> in aurora: simultaneous space-borne and ground-based measurements and modeling results

2014 ◽  
Vol 32 (5) ◽  
pp. 499-506 ◽  
Author(s):  
K. Axelsson ◽  
T. Sergienko ◽  
H. Nilsson ◽  
U. Brändström ◽  
K. Asamura ◽  
...  
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Electron Flux ◽  
Imaging System ◽  
Electron Excitation ◽  
Absolute Calibration ◽  
Simultaneous Measurements ◽  
Auroral Emission ◽  
Negative System ◽  
Correct Comparison

Abstract. The auroral emission of the first negative system of N2+ at 427.8 nm is analyzed using simultaneous measurements from the ground with ALIS (Auroral Large Imaging System) and from space with optical (MAC) and particle (ESA) instruments of the Reimei satellite. The study has two main objectives. The first is validation of the absolute calibration of the ALIS and the Reimei MAC cameras. The other task is to evaluate different cross sections of the electron excitation of N2+ that are used for the modeling of the auroral 1N system emissions. The simultaneous measurements of the 427.8 nm emission by ALIS and Reimei imagers show excellent agreement, indicating that the calibration of the two instruments is correct. Comparison of the 427.8 nm emission intensity calculated using the incident electron flux measured by the Reimei particle instruments with intensities measured by the optical imagers show that the best match is reached with the cross section from Shemansky and Liu (2005).

Absolute, cascade-free cross sections for the2S→2Ptransition inZn+using electron-energy-loss and merged-beams methods

1991 ◽  
Vol 67 (1) ◽  
pp. 30-33 ◽  
Author(s):  
Steven J. Smith ◽  
K-F. Man ◽  
R. J. Mawhorter ◽  
I. D. Williams ◽  
A. Chutjian
Keyword(s):  
Energy Loss ◽  
Electron Energy ◽  
Cross Sections ◽  
Electron Energy Loss

Electron Scattering in Superconducting Oxides

1987 ◽  
Vol 99 ◽  
Author(s):  
J. Ruvalds ◽  
Y. Ishu
Keyword(s):  
Transition Temperature ◽  
Energy Loss ◽  
Cross Section ◽  
Electron Scattering ◽  
Superconducting Transition Temperature ◽  
Alloy Composition ◽  
Superconducting Transition ◽  
Highly Sensitive ◽  
Superconducting Oxides ◽  
Electron Energy Loss

ABSTRACTElectron energy loss measurements on superconducting oxides are correlated with an acoustic plasm on branch whose energy and width is highly sensitive to the alloy composition. Changing oxygen content reveals structure in the electron cross section which tracks the changes in the superconducting transition temperature.

Sign in / Sign up

Export Citation Format

Share Document