Article

1998 ◽  
Vol 76 (2) ◽  
pp. 153-162
Author(s):  
P Kurunczi ◽  
K Becker ◽  
K Martus
Keyword(s):  
Hydrogen Atom ◽  
Organic Compounds ◽  
Cross Sections ◽  
Impact Energy ◽  
Atomic Hydrogen ◽  
Vacuum Ultraviolet ◽  
The Other ◽  
Dissociative Excitation ◽  
Balmer Series ◽  
Break Up

The vacuum ultraviolet (VUV) emissions of the hydrogen Lyman series following the dissociative excitation of the Si-organic compounds tetraethoxysilane (TEOS), tetramethylsilane (TMS), and hexamethyldisiloxane (HMDSO) by controlled electron impact were analyzed. Absolute photoemission cross sections from threshold to 200 eV and appearance potentials were determined for the Lyman-α and Lyman-β emissions for each of the three targets. The measured apparent emission cross sections at 100 eV impact energy for the Lyman-α lines are 6.0 x 10-19 cm2 for TMS, 6.5 x 10-19 cm2 for HMDSO and 1.1 x 10-18 cm2 for TEOS. The apparent Lyman-α cross sections for all three targets contained significant cascade contributions from the H Balmer series. Detailed studies of the near threshold regions indicated that several break-up mechanisms of the parent molecules contribute to the emissions. The lowest onsets for HMDSO, and TEOS were attributed to the removal of a single excited atomic hydrogen atom in the n=2 state. Additional onsets at higher energies could not be uniquely correlated in all cases with a particular break-up channel and (or) cascading, since the other fragments in these processes were not identified. The Lyman-β apparent emission cross sections were also measured and we found values of 1.3 x 10-19 cm2 for TMS, 1.6 x 10-19 cm2 for HMDSO, and 2.0 x 10-19 cm2 for TEOS at an impact energy of 100 eV. PACS Nos. 52.20Fs and 34.80Gs

A study of the properties of hydrogen films on tungsten by the method of contact potentials

1937 ◽  
Vol 33 (3) ◽  
pp. 394-402 ◽  
Author(s):  
R. C. L. Bosworth
Keyword(s):  
Dipole Moment ◽  
Hydrogen Atom ◽  
Gas Phase ◽  
Atomic Hydrogen ◽  
The Other ◽  
Condensation Coefficient ◽  
Effective Dipole Moment ◽  
Tungsten Atom ◽  
Contact Potential ◽  
Hydrogen Molecules

In a study of the properties of hydrogen on tungsten by the method of contact potentials the following points have been established:(1) The contact potential of a 92% covered surface of hydrogen on tungsten against bare tungsten is 1·04 V., and the Richardson constants for such a surface are, approximately,A = 30, b = 5·60 V.(2) A film of deuterium is 20 m V. positive relative to a similar hydrogen film.(3) Over the range of temperatures and pressures used by Bryce in a study of the production of atomic hydrogen the films are nearly saturated, so that the production of atomic hydrogen is primarily due to a molecule striking a bare tungsten atom, one atom being adsorbed and the other going into the gas phase.(4)The condensation coefficient for hydrogen molecules on cold tungsten is 0·01.(5) The effective dipole moment of each hydrogen atom on the surface is −0·42 Debye unit and is independent of the fraction of the surface covered.

Vacuum Ultraviolet Photoionization Mass Spectra and Cross-Sections for Volatile Organic Compounds at 10.5 eV

2007 ◽  
Vol 61 (8) ◽  
pp. 896-902 ◽  
Author(s):  
Nozomu Kanno ◽  
Kenichi Tonokura
Keyword(s):  
Volatile Organic Compounds ◽  
Organic Compounds ◽  
Cross Sections ◽  
Mass Spectra ◽  
Vacuum Ultraviolet ◽  
Single Photon ◽  
Photoionization Cross Section ◽  
Oxygenated Compounds ◽  
Flight Mass Spectrometry ◽  
Volatile Organic

Vacuum ultraviolet single-photon ionization time-of-flight mass spectrometry (VUV-SPI-TOFMS) has been applied to the detection of volatile organic compounds (VOCs), including aromatic, chlorinated, and oxygenated compounds. Photoionization mass spectra of 23 VOCs were measured using SPI-TOFMS at 10.5 eV (118 nm). The limits of detection of VOCs using SPI-TOFMS at 10.5 eV were estimated to be a few ppbv. The mass spectra of 20 VOCs exhibit only the parent ion and its isotopes' signals. The ionization processes of the VOCs were discussed on the basis of the reaction enthalpies predicted by the quantum chemical calculations. Absolute photoionization cross-sections for 23 VOCs, including 12 newly measured VOCs, at 10.5 eV were determined in comparison to the reported absolute photoionization cross-section of NO.

Excitation of the 21S and 23S states of helium atoms by electron and hydrogen atom impact

1977 ◽  
Vol 55 (5) ◽  
pp. 396-402 ◽  
Author(s):  
Madeleine M. Felden ◽  
Marceau A. Felden
Keyword(s):  
Hydrogen Atom ◽  
Cross Sections ◽  
Ground State ◽  
Wave Functions ◽  
The Other ◽  
Helium Atoms ◽  
Atomic Wave ◽  
Excitation Cross Sections ◽  
The One ◽  
S States

Ochkur's approximation is used to analyse the excitation of 21S and 23S levels of helium atoms from the ground state by electron and hydrogen atom impact. Calculations are made with different atomic wave functions. To characterize the 11S and 21S states we use, on the one hand, the wave functions of Byron and Joachain, on the other hand, those of Hylleraas and Marriott and Seaton. For the 11S and 23S states, calculations are made firstly with the wave functions of Byron and Joachain and Morse, Young, and Haurwitz, secondly with those of Shull and Lödwin. Numerical values are tabulated and compared in each case. The discrepancies show the importance of the choice of atomic wave functions in the calculation of the excitation cross sections. Available experimental data and corresponding theoretical values obtained from other theories are plotted and compared with the present results.

Ionization of Organic Molecules Using Coherent Vacuum Ultraviolet Light

1989 ◽  
Vol 43 (7) ◽  
pp. 1211-1214 ◽  
Author(s):  
J. H. Arps ◽  
C. H. Chen ◽  
M. P. McCann ◽  
I. Datskou
Keyword(s):  
Organic Compounds ◽  
Ultraviolet Light ◽  
Harmonic Generation ◽  
Cross Sections ◽  
Mass Spectra ◽  
Vacuum Ultraviolet ◽  
Organic Molecules ◽  
Impact Ionization ◽  
Third Harmonic Generation ◽  
Third Harmonic

Third harmonic generation in xenon was used to produce vacuum ultraviolet light at a fixed wavelength of 118 nm. These photons were able to ionize a number of organic molecules with negligible yields of fragmentation ions. This method yielded far simpler mass spectra than those utilizing electron impact ionization. Absolute photoionization cross sections were measured for six organic compounds at 118.2 nm.

scholarly journals Production of O(1D) following electron impact on CO2

2013 ◽  
Vol 91 (12) ◽  
pp. 1044-1048 ◽  
Author(s):  
W. Kedzierski ◽  
J.D. Hein ◽  
C.J. Tiessen ◽  
D. Lukic ◽  
J.A. Trocchi ◽  
...  
Keyword(s):  
Energy Range ◽  
Electron Impact ◽  
Cross Sections ◽  
Impact Energy ◽  
Production Cross ◽  
Threshold Energy ◽  
Dissociative Excitation ◽  
Pulsed Electron Beam ◽  
Exciting Electron ◽  
Relative Production

We have studied the excitation of metastable O(1D) following dissociative excitation of CO2 in the electron impact energy range from threshold to 400 eV. A solid Ne matrix at ∼20 K forms the heart of the detector. This is sensitive to the metastable species through the formation of excited excimers (NeO*), The resultant excimer radiation is readily detected, providing a means of measuring the production of the metastables. Using a pulsed electron beam and time-of-flight techniques, we have measured the O(1D) kinetic energy spectrum and its relative production cross sections as a function of electron impact energy. Threshold energy data are used to gain information about the excitation channels involved. In addition, an emission excitation function for the red photons, emitted in coincidence with the exciting electron pulse, has been measured in the 0–400 eV energy range.

Vacuum ultraviolet emissions of trifluoromethane following electron impact in the wavelength range 50–130 nm

1989 ◽  
Vol 67 (7) ◽  
pp. 694-698 ◽  
Author(s):  
Shouye Wang ◽  
J. W. McConkey
Keyword(s):  
Electron Impact ◽  
Wavelength Range ◽  
Cross Sections ◽  
Incident Energy ◽  
Vacuum Ultraviolet ◽  
Neutral Hydrogen ◽  
Dissociative Excitation ◽  
Hydrogen Atoms ◽  
Threshold Excitation ◽  
Ultraviolet Emissions

The dissociative excitation of CF3H by electron impact has been studied under single collision conditions for incident energies up to 600 eV. The emission spectrum in the wavelength range 50–130 nm shows many features arising from neutral and singly ionized fluorine and carbon fragments, as well as from neutral hydrogen atoms. Absolute cross sections for the observed features were measured at 200 eV incident energy, while the excitation functions of the most intense emissions were studied over the whole energy range. The threshold excitation of the hydrogen Lyman α line displays onsets at 18.4 and 34.0 eV, while that of the fluorine F I 95.5 nm feature shows only one onset at 33.0 eV. Possible dissociation channels are discussed.

scholarly journals On the secondary spectrum of hydrogen

1920 ◽  
Vol 96 (679) ◽  
pp. 382-388 ◽  
Keyword(s):  
Hydrogen Atom ◽  
Relative Intensity ◽  
Fundamental Difference ◽  
The Other ◽  
Pure Hydrogen ◽  
Balmer Series ◽  
Reduced Pressure ◽  
Theoretical Investigations ◽  
Abundant Evidence ◽  
Great Complexity

Theoretical investigations of the origin of spectra in relation to the structure of the atom have concentrated especially on the spectrum of hydrogen, on account of the supposed simplicity of the hydrogen atom. They have, however, been confined almost exclusively to the Balmer series, and have ignored the difficulties which arise from the fact that hydrogen possesses another spectrum, usually known as the secondary spectrum, which is of great complexity, and the co-ordination of whose lines into recognised bands or series of lines is still in a very unfinished state. The investigations of Buisson and Fabry, in which the physical widths of spectrum lines were measured with the interferometer, refer at least a part of the lines of the secondary spectrum to the hydrogen atom, and the complications introduced into theoretical investigations cannot therefore be impartially waived by the assumption that the molecule is concerned in the production of the secondary spectrum. As regards the relation of the two spectra, there is abundant evidence of a fundamental difference in their origin. In many celestial spectra the lines of the Balmer series constitute one of the most prominent features, whilst the identification of lines of the secondary spectrum is at least extremely doubtful. In the laboratory it has long been known that the relative intensity of the secondary spectrum is greatly reduced by the presence of impurities, notably oxygen, in vacuum tubes containing hydrogen, and by the passage of powerful condensed discharges. On the other hand, under conditions in which an uncondensed discharge from an induction coil is passed through very dry and pure hydrogen at a reduced pressure, the lines of the secondary spectrum may rival those of the Balmer series in intensity.

Electron Irradiation Effects in Polyoxymethylene Crystals Grown Inside Trioxane Crystals

1971 ◽  
Vol 29 ◽  
pp. 78-79
Author(s):  
J. P. Colson ◽  
D. H. Reneker
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Detailed Examination ◽  
The Other ◽  
Electron Micrograph ◽  
Irradiation Effects ◽  
Threefold Axis ◽  
Typical Sample ◽  
Polymer Crystals ◽  
Chain Axis

Polyoxymethylene (POM) crystals grow inside trioxane crystals which have been irradiated and heated to a temperature slightly below their melting point. Figure 1 shows a low magnification electron micrograph of a group of such POM crystals. Detailed examination at higher magnification showed that three distinct types of POM crystals grew in a typical sample. The three types of POM crystals were distinguished by the direction that the polymer chain axis in each crystal made with respect to the threefold axis of the trioxane crystal. These polyoxymethylene crystals were described previously.At low magnifications the three types of polymer crystals appeared as slender rods. One type had a hexagonal cross section and the other two types had rectangular cross sections, that is, they were ribbonlike.

Removal of Trace Metals From Wastewater by Activated Carbon

1973 ◽  
Vol 8 (1) ◽  
pp. 110-121
Author(s):  
A. Netzer ◽  
J.D. Norman
Keyword(s):  
Activated Carbon ◽  
Trace Metals ◽  
Organic Compounds ◽  
The Other ◽  
Published Data ◽  
Ph Adjustment ◽  
Nickel Silver ◽  
Ph Range ◽  
Carbon Treatment ◽  
Cobalt Copper

Abstract The merits of activated carbon for removal of organic compounds from wastewater have been well documented in the literature. On the other hand there is a lack of published data on the use of activated carbon for the removal of trace metals from wastewater. Experiments were designed to assess the possibility that activated carbon treatment would remove aluminum, cadmium, chromium, cobalt, copper, iron, lead, manganese, mercury, nickel, silver and zinc from wastewater. All metals studied were tested over the pH range 3-11. Greater than 99.5% removal was achieved by pH adjustment and activated carbon treatment for most of the metals tested.

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