IONIZATION PROBABILITY CURVES USING AN ELECTRON SELECTOR: RESULTS ON N2+, N+, Xe++

1954 ◽  
Vol 32 (12) ◽  
pp. 764-774 ◽  
Author(s):  
E. M. Clarke
Keyword(s):  
Electron Energy ◽  
Mass Spectrometer ◽  
Ionization Probability ◽  
Yield Curves ◽  
Ionization Yield

An apparatus consisting of an electron energy selector built into a mass spectrometer is described. With it, initial ionization yield curves may be obtained. The interpretation of these curves is discussed, and the following new measurements reported:[Formula: see text]

Multiple ionization of the rare gases by successive electron impacts (0–250 eV). II. 1S–2S transition in 3He+

1968 ◽  
Vol 46 (7) ◽  
pp. 865-869 ◽  
Author(s):  
P. A. Redhead ◽  
S. Feser
Keyword(s):  
Electron Energy ◽  
Cross Section ◽  
Mass Spectrometer ◽  
Ion Current ◽  
Rare Gases ◽  
Close Coupling ◽  
Trapped Ion ◽  
Multiple Ionization ◽  
Electron Impacts ◽  
Autoionizing States

The tertiary collision sequence of electrons with helium (He → He+ → He+m(2S) → He2+) has been observed with a trapped-ion mass spectrometer. The variation of He2+ ion current with electron energy shows a threshold at 40.8 eV, and structure, which results from excitation to autoionizing states of the atom below the n = 3 threshold of He+, is observed in the range 45–49 eV. Estimates of the cross section for the 1S–2S transition in He+ lie slightly below the values from close-coupling calculations.

A device for controlling the energy of ionizing electrons in the low-energy range designed to form a complete mass spectrum of negative ions using a quadrupole mass spectrometer

2020 ◽  
Vol 86 (4) ◽  
pp. 12-20
Author(s):  
A. G. Terentyev ◽  
R. V. Khatymov ◽  
A. V. Maltsev
Keyword(s):  
Mass Spectrum ◽  
Energy Range ◽  
Electron Energy ◽  
Mass Spectrometer ◽  
Mass Spectra ◽  
Negative Ions ◽  
Mass Spectrometric ◽  
Low Energy ◽  
Quadrupole Mass ◽  
Positive Ions

Operation with positive ions formed from the impact of high energy electrons (usually 70 eV, which exceeds the ionization energy of the molecules) is a standard mode for mass spectrometric detectors of most gas chromatography-mass spectrometric complexes (GC/MS) in the basic configuration. At the same time, we have shown that the option of setting the energy of ionizing electrons (maintained in the design of some serial devices) within the pre-ionization region also allows one to obtain mass spectra of negative ions (NI) which, in turn, significantly expands the analytical potential of standard equipment. The formation of NI occurs in the low-energy range of 0 – 15 eV due to resonant capture of electrons by molecules (REC). In contrast to positive ions, the intensity of NI formation sharply (resonantly) depends on the electron energy and this dependence is characteristic of each chemical compound. Both the relative intensity of the mass-peaks and, in general, the ionic composition of the formed mass spectrum of NI significantly depend on the electron energy. The problem of choosing the optimal energy of ionizing electrons providing the same efficiency of mass-spectrometric determination of all components of complex mixtures of dissimilar compounds is also associated with the features of negative ion formation during chromatography-mass spectrometric analysis. To address the problem, we propose a technique providing generation of complete (in NI composition and intensities) mass spectra of NI through repeated variation of the energy of ionizing electrons in a given range of 0 – 10 eV. Technical implementation of the technique [1] was carried out at the Design Bureau «Chromatec «(Yoshkar Ola, Russia) in the form of a special electronic device, which was tested in pilot operation as part of the gas chromatograph complex with a quadrupole mass spectrometer «Chromatec». We describe the principle of operation of the device and present the results of tests.

Transmission optimization of a microprobe instrument using a magnetic mass spectrometer

1992 ◽  
Vol 50 (2) ◽  
pp. 1546-1547
Author(s):  
Georges Slodzian ◽  
Bernard Daigne ◽  
Francois Girard
Keyword(s):  
Mass Spectrometer ◽  
Ionic Species ◽  
Ionization Probability ◽  
High Mass ◽  
Secondary Ion Emission ◽  
High Ionization ◽  
Ion Emission ◽  
Primary Ions ◽  
Secondary Ion ◽  
Useful Yield

Secondary ion emission from a solid target bombarded with primary ions in the range of several keV energy is a well known phenomenon which has been extensively used for determining elemental and isotopic compositions of solid samples and characterizing surface layers. Taking advantage of the fact that secondary ion emission is a rather localized process and has relatively high ionization yields, it is possible to build analytical ion microscopes with resolutions better than l00nm and fairly good sensitivity. The ionization useful yield (inverse of the average number of target atoms which must be sputtered to produce a well identified ion) depends upon the ionization probability and the overall transmission of the instrument (ratio of the number of ions forming a line in the mass spectrometer to the number of ions produced when a given number of atoms have been sputtered). It should be emphasized that the useful yield controls the ultimate performances of the instrument and that transmission considerations are essential when the spectrometer must work at high mass resolutions to separate different ionic species having the same number of mass units.

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.

Trends in Electron Energy Loss Spectroscopy

1977 ◽  
Vol 35 ◽  
pp. 228-229
Author(s):  
C. Colliex ◽  
P. Trebbia
Keyword(s):  
Energy Loss ◽  
Electron Energy ◽  
Electron Energy Loss Spectroscopy ◽  
Materials Science ◽  
Analytical Technique ◽  
Recent Developments ◽  
Quantitative Results ◽  
Electron Microscopes ◽  
Electron Energy Loss ◽  
Primary Electrons

The physical foundations for the use of electron energy loss spectroscopy towards analytical purposes, seem now rather well established and have been extensively discussed through recent publications. In this brief review we intend only to mention most recent developments in this field, which became available to our knowledge. We derive also some lines of discussion to define more clearly the limits of this analytical technique in materials science problems.The spectral information carried in both low ( 0<ΔE<100eV ) and high ( >100eV ) energy regions of the loss spectrum, is capable to provide quantitative results. Spectrometers have therefore been designed to work with all kinds of electron microscopes and to cover large energy ranges for the detection of inelastically scattered electrons (for instance the L-edge of molybdenum at 2500eV has been measured by van Zuylen with primary electrons of 80 kV). It is rather easy to fix a post-specimen magnetic optics on a STEM, but Crewe has recently underlined that great care should be devoted to optimize the collecting power and the energy resolution of the whole system.

Sign in / Sign up

Export Citation Format

Share Document