<i>Electronic and Ionic Impact Phenomena</i>

Massey, H. S. W.; Burhop, E. H. S.; Morse, Philip Μ.

doi:10.1063/1.3061100

Cited by 200 publications

(49 citation statements)

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“…8-10 shows that it decreases with increasing incident beam energy, becoming a shoulder in the elastic peak when this energy reaches 75 eV. This is expected for spin-forbidden transitions 2 and is consistent with Evans' assignment. A similar comparison between the 6-5 eV and 7.7 eV peak intensities shows that their ratio does not decrease to any significant extent in the 40 eV to 75 eV range of incident electron energies used, suggesting that the 6.5 peak, although optically forbidden, does not correspond to a singlet-triplet transition?…”

Section: Excitation Spectra Of Ethylenesupporting

confidence: 71%

Electron-impact spectroscopy

Kuppermann¹,

Raff²

1963

Discuss. Faraday Soc.

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A spectrometer has been devised for determining electronic energy levels of molecules by inelastic scattering of low-energy electrons. It permits the detection of optically forbidden electronic transitions as clearly as optically allowed ones in a routine manner. The spectrometer has been used to obtain excitation spectra for helium, argon, hydrogen and ethylene. For the first three of these substances, the spectra agree with previous experiments. For ethylene, in addition to optically allowed transitions, two forbidden ones occur at about 4-6 and 6-5eV. Variation of peak heights with incident electron beam energy suggest that the first corresponds to a triplet state but that the second does not.Franck and Hertz1 used the measurement of energy losses of electron swarms in atomic gases as a means of determining the lowest excitation energies of those gases. However, such electron-impact techniques have not been used to any appreciable extent for the determination of electronic energy levels of molecules. The reasons are : first, because electrons can produce rotational and vibrational excitation of the ground electronic states of molecules, it is not possible to use experimental techniques in which the electrons build up energy slowly between collisions if one wishes to determine the electronic levels of those molecules. Therefore, one must use single-scattering electron beam techniques, which require more elaborate set-ups. Secondly, because of the relatively simple optical techniques which permit great accuracy in the determination of photon energies, optical spectroscopy provides a simpler method of much higher resolution for the measurement of electronic transitions in atoms and molecules.The development of metal high vacuum techniques and of electronic circuitry have simplified the construction and operation of single-scattering electron-impact spectrometers. In addition, there exists an extremely powerful reason for using low-energy electron impact as a spectroscopic tool. This is the difference in the selection rules for excitation of electronic energy levels of atoms and molecules by photons and by electrons. Practically all electronic transitions are allowed when low-energy electrons are used.2 They include transitions which are spin-forbidden and/or symmetry-forbidden when photons are used. Therefore, low-energy electronimpact spectroscopy provides in principle a technique which permits determination of such optically forbidden electronic transitions, as well as optically allowed ones. In addition, transition energies above 11 eV, which are difficult to deal with optically, can be easily studied with electron-impact techniques.The inelastic scattering of low-energy electrons by molecules has been experimentally studied by a number of researchers. The molecules studied include hydrogen,3 oxygen,4 nitrogen,s carbon monoxide 6 and carbon dioxide.6 However, most studies were directed either to the measurement of scattering cross-sections or to the determination of the appearance potentials of assorted ions....

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Section: Excitation Spectra Of Ethylenesupporting

confidence: 71%

Electron-impact spectroscopy

Kuppermann¹,

Raff²

1963

Discuss. Faraday Soc.

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“…1) and electrode (23) exceeds 20 V, the current I of nonself-sustained discharge and velocity dI/dU both grow again due to the gas ionization by electrons emitted by the chamber (1) and accelerated in the sheath (27) up to energy eU exceeding the ionization threshold E i = 15.8 eV of nitrogen [20]. At one and the same U value velocity dI/dU is rising when the beam equivalent current I b and/or its energy E b are growing (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…The energy of ions (9) is regulated using high-voltage power supply (18), the beam current is regulated using power supply (19) between anode (3) and cathode (2). Ion current in the circuit of cathode (2) is measured with ammeter (20) and cathode fall of potential is controlled with voltmeter (21).…”

Section: Methodsmentioning

confidence: 99%

Sharpening of ceramic knife-edges and production of plasma for cutting tools nitriding with the use of a broad fast molecule beam

Metel

2016

Mechanics & Industry

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-A source of gas molecules with energy ranging from 0.5 up to 4 keV has been used for production of non-self-sustained glow discharge plasma. Cutting tools immersed in nitrogen plasma are heated by the fast molecules but they are not sputtered by ions from the plasma. During nitriding of a tool the fast molecules sputter its cutting edges with the same rate as the rest of the tool surface. It results in a decrease of the edge radius. For sharpening of ceramic knife-edges were used fast neutral argon atoms, which sputter materials more intensively than nitrogen molecules.

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“…In the next decades, the investigations continued (for reviews, see Massey and Burhop 1952;Allison and Warshaw 1953) and were also extended to astrophysical scenarios. Perhaps the first of these investigations was devoted to comets: Biermann (1953) suggested that the CO + ions observed in their tails might be predominantly the result of charge transfer reactions between solar wind protons and neutral cometary CO molecules, and Harwit and Hoyle (1962) concluded that charge transfer may lead to the formation of a magnetic barrier around the cometary nucleus.…”

Section: The Situation Before 1996mentioning

confidence: 99%

Charge Transfer Reactions

Dennerl

2010

Space Sci Rev

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Charge transfer, or charge exchange, describes a process in which an ion takes one or more electrons from another atom. Investigations of this fundamental process have accompanied atomic physics from its very beginning, and have been extended to astrophysical scenarios already many decades ago. Yet one important aspect of this process, i.e. its high efficiency in generating X-rays, was only revealed in 1996, when comets were discovered as a new class of X-ray sources. This finding has opened up an entirely new field of X-ray studies, with great impact due to the richness of the underlying atomic physics, as the X-rays are not generated by hot electrons, but by ions picking up electrons from cold gas. While comets still represent the best astrophysical laboratory for investigating the physics of charge transfer, various studies have already spotted a variety of other astrophysical locations, within and beyond our solar system, where X-rays may be generated by this process. They range from planetary atmospheres, the heliosphere, the interstellar medium and stars to galaxies and clusters of galaxies, where charge transfer may even be observationally linked to dark matter. This review attempts to put the various aspects of the study of charge transfer reactions into a broader historical context, with special emphasis on X-ray astrophysics, where the discovery of cometary X-ray emission may have stimulated a novel look at our universe.

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Electronic and Ionic Impact Phenomena

Cited by 200 publications

References 0 publications

Electron-impact spectroscopy

Electron-impact spectroscopy

Sharpening of ceramic knife-edges and production of plasma for cutting tools nitriding with the use of a broad fast molecule beam

Charge Transfer Reactions

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