Low-voltage electron impact

Table X. Comparison of Field Ionization and Low-Voltage Electron-Impact Mass Spectral Results for Two Adsorption Concentrates,...

T. D. Perreira, N. B. Determination of Field-Ionization Relative Sensitivities for the Analysis of Coal-Derived Liquids and Their Correlation with Low-Voltage Electron-Impact Relative Sensitivities. Anal. Chem., 1976, 45 (14), 2105-2113. 

Mass spectral data were obtained for the various oil and asphaltene aromatic fractions using a CEC 21-110B mass spectrometer equipped with a modified combination field-ionization/electron-impact (FI/EI) ion source and for the asphaltene fractions using a KRATOS MS-50 mass spectrometer equipped with a low-voltage electron-impact (LV/EI) ion source. With the former instrument, 70-eV EI/MS were recorded at a static resolution of approximately 21,000 on Ilford Q2 photographic plates, and FI/MS were produced with an emitter potential of 5.8 kV and a counterelectrode potential of +800 V to —800 V. Low-resolution FI/MS were... 

Precise molecular-ion masses obtained by both 70-eV and low-voltage electron-impact-induced ionization revealed the presence of compounds adhering to the general formula CnH2n+zNaOfcSc where Z(H,Na,Ofc,Sc) is the specific-Z value (compound type) and 0 < a < 1, 0 < < 4, and 0 < c < 1. Equation 1 expresses the weight percent (WP)... 

Budzikiewicz, H., Poppe, A. Low voltage electron impact mass spectra of aromatic esters. 

The most common conventional gas source is an electron impact (El) source. This consists of a metal chamber with a volume of a few cm3, through which the sample flows in the form of a gas. Electrons produced by thermionic emission from a heated tungsten filament are passed through this gas, and accelerated by a relatively low voltage ( 100eV), causing ionization within the sample gas. A plate inside the chamber carries a low positive potential (the repeller ) which ejects the positive ions into a region which contains a series of plates (called lenses) and slits, which serve to focus, collimate, and accelerate the ion beam into the next part of the system... 

This is because the total secondary emission yield a (number of secondary electrons created per incident electron) varies with beam energy so that charge equilibrium (a equal to 1) is created, regardless of the material analysed, for a low voltage of approximately 1 to 2 kV (Fig. 7.8). Beyond this voltage level, the number ofmeident electrons exceeds the number of electrons emitted and, in the case of an insulating material, these electrons accumulate in the impact zone and make observation impossible. 

TC Yu. Impact modification of polypropylenes. Proceedings of Society of Plastics Engineers Annual Technical Conference, San Francisco, 1994, pp 2439-2445. GM Brown, JH Butler. New method for the characterization of domain morphology of polymer blends using ruthenium tetroxide staining and low voltage scanning electron microscopy (LVSEM). Polymer 38 3937-3945, 1997. 

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