Primary processes in the formation of hydrogen atoms in the radiolysis of water vapor

1967 ◽  
Vol 71 (4) ◽  
pp. 1118-1123 ◽  
Author(s):  
George R. A. Johnson ◽  
Miomir Simic
Keyword(s):  
Water Vapor ◽  
Hydrogen Atoms

Fluorescence Emission of Excited Hydrogen Atoms after Core Excitation of Water Vapor

2006 ◽  
Vol 96 (6) ◽  
Author(s):  
E. Melero García ◽  
A. Kivimäki ◽  
L. G. M. Pettersson ◽  
J. Álvarez Ruiz ◽  
M. Coreno ◽  
...  
Keyword(s):  
Water Vapor ◽  
Fluorescence Emission ◽  
Hydrogen Atoms ◽  
Core Excitation

An Overview of Aeronomic Processes in the Stratosphere and Mesosphere

1974 ◽  
Vol 52 (8) ◽  
pp. 1381-1396 ◽  
Author(s):  
M. Nicolet
Keyword(s):  
Nitric Oxide ◽  
Water Vapor ◽  
Nitric Acid ◽  
Oxygen Atom ◽  
Eddy Diffusion ◽  
Atmospheric Conditions ◽  
Hydrogen Atoms ◽  
Electronically Excited ◽  
The Vertical Distribution ◽  
Excited Oxygen

The discrepancy noted between theoretical and observational concentrations of O3 in the mesosphere and stratosphere can be explained by an effect of hydrogen compounds and of nitrogen oxides. Solar radiation dissociates water vapor and methane in the thermosphere and upper mesosphere. In the stratosphere the reaction of the excited oxygen atom O(1D) with methane and nitrous oxide leads to a destruction of these two molecules in the stratosphere which corresponds to a production of carbon monoxide with water vapor and of nitric oxide, respectively. Hydrogen and water vapor molecules also react with the electronically excited oxygen atom O(1D) leading to hydroxyl radicals. Insitu sources of H2 exist in the stratosphere and mesosphere: reaction of OH with CH1, photodissociation of formaldehyde, and also reaction between hydroperoxyl radicals and hydrogen atoms. The vertical distribution of water vapor is not affected by its dissociation in the stratosphere and mesosphere since its reformation is rapid.The ratio of the hydroxyl and hydroperoxyl radical concentrations cannot be determined with adequate precision and complicates the calculation of the destruction of ozone which occurs through reactions of OH and HO2 not only with atomic oxygen at the stratopause but also directly in the middle stratosphere and with CO and NO in the lower stratosphere.In addition to the various reactions involving nitric oxide and nitrogen dioxide, the reactions leading to the production and destruction of nitric acid and nitrous acid must be considered. Nitric acid molecules are involved in an eddy diffusion transport from the lower stratosphere into the troposphere and are, therefore, responsible for the removal of nitric oxide which is produced in the stratosphere. Atmospheric conditions must be known at the tropopause.

The X-radiolysis of water vapor containing methanol. Effects of some electron and hydrogen atom scavengers

1968 ◽  
Vol 46 (12) ◽  
pp. 1957-1964 ◽  
Author(s):  
R. S. Dixon ◽  
M. G. Bailey
Keyword(s):  
Nitrous Oxide ◽  
Water Vapor ◽  
Carbon Tetrachloride ◽  
Hydrogen Atom ◽  
Sulfur Hexafluoride ◽  
Hydrogen Yield ◽  
Hydrogen Atoms ◽  
A Value ◽  
Ion Recombination ◽  
Positive Ion

The X-radiolysis of water vapor containing methanol at 125 °C and 1 atm pressure has been studied alone and in the presence of some electron and hydrogen atom scavengers. In water vapor containing methanol only, a plateau value G(H2) = 7.9 ± 0.3 is obtained at all methanol concentrations above 0.5 mole %. Addition of propylene drastically reduces this yield due to efficient scavenging of hydrogen atoms, and values for the total number of H atoms from all precursors g(H)t = 7,5 ± 0.2 and [Formula: see text] are deduced from the competition. An unscavengeable hydrogen yield g(H2) ~ 0.5 is also indicated in mixtures containing propylene. Nitrous oxide and sulfur hexafluoride are found to scavenge electrons efficiently in water vapor containing methanol and the number of hydrogen atoms arising from electron–positive ion recombination is estimated to have a value G = 2.2 ± 0.6. The number of hydrogen atoms arising from processes not involving electrons is g(H) = 5.2 ± 0.3. Carbon tetrachloride reacts efficiently with both electrons and hydrogen atoms, with k(H + CH3OH)/k(H + CCl4) = 0.085. Values of g(H) = 4.9 ± 0.5 and g(H2) = 0.8 ± 0.2 are deduced from mixtures containing carbon tetrachloride.

scholarly journals The distribution and saturation of water vapor as inferred from ACS during the first Martian year of TGO Science observations

2020 ◽  
Author(s):  
Anna Fedorova ◽  
Franck Montmessin ◽  
Oleg Korablev ◽  
Mikhail Luginin ◽  
Alexander Trokhimovskiy ◽  
...  
Keyword(s):  
Water Vapor ◽  
Vertical Distribution ◽  
Water Vapour ◽  
Atmospheric Chemistry ◽  
Water Distribution ◽  
Water Cycle ◽  
First Year ◽  
Hydrogen Atoms ◽  
Saturation State ◽  
Water Ice

<p>The water vapour vertical distribution is an eloquent gauge of the relative roles of the various sources, sinks and processes that control the Martian water cycle. However, its behaviour is still poorly studied while it is instrument for our understanding of the loss of water from Mars to space, which results from the transport of water to the upper atmosphere where it is disassociated to hydrogen atoms that later escape. We use the Atmospheric Chemistry Suite on the ExoMars Trace Gas Orbiter to characterize the water distribution with altitude. Here we present results of the Atmospheric Chemistry Suite (ACS) instrument NIR channel for the first year of TGO observations covering the almost full year from Ls 160° of the Martian year 34 (April 2018) to Ls 130° of the Martian year 35 (January 2020). Simultaneous measurements of the water vapour mixing ratio, temperature and dust vertical distribution and formation of water ice clouds allow us to constrain the complex water behaviour and estimate the saturation state of H2O. Water profiles during the 2018-2019 southern spring and summer stormy seasons show that high altitude water is preferentially supplied close to perihelion and that large supersaturation occurs even when clouds are present. Here we attempt to complete the story by studying water vapor during the northern spring and summer to explore whether saturation impacts water transport between hemispheres in this season. The data analysis of MY35 was supported by RSF (project No. 20-42-09035).</p>

High-Temperature Environmental Embrittlement of Thermomechanically Processed TiAl-Based Intermetallic Alloys with Various Kinds of Microstructures

2004 ◽  
Vol 842 ◽  
Author(s):  
T. Takasugi ◽  
Y. Hotta ◽  
S. Shibuya ◽  
Y. Kaneno ◽  
H. Inoue ◽  
...  
Keyword(s):  
Water Vapor ◽  
High Temperature ◽  
Intermetallic Alloy ◽  
Hydrogen Gas ◽  
Tensile Fracture ◽  
Intermetallic Alloys ◽  
Hydrogen Atoms ◽  
Environmental Media ◽  
Environmental Embrittlement ◽  
Higher Temperature

ABSTRACTThermomechanically processed TiAl-based intermetallic alloys with various alloy compositions and microstructures were tensile tested in various environmental media including air, water vapor and a mixture gas of 5vol.%H2+Ar as a function of temperature. All the TiAl-based intermetallic alloys showed reduced tensile fracture stress (or elongation) in air, water vapor and a mixture gas of 5vol.%H2+Ar not only at ambient temperature (RT∼600K) but also at high temperature mostly from 600K to 1000K (sometimes higher temperature than 1000K). The high-temperature environmental embrittlement of TiAl-based intermetallic alloy depended upon the microstructure. The possible species causing the high-temperature environmental embrittlement are hydrogen atoms decomposed from water vapor (H2O) or hydrogen gas (H2), similar to those causing the low-temperature environmental embrittlement.

STUDIES ON HYDROGEN–OXYGEN SYSTEMS IN THE ELECTRIC DISCHARGE: I. THE REACTIONS OF HYDROGEN ATOMS WITH HYDROGEN PEROXIDE

1966 ◽  
Vol 44 (8) ◽  
pp. 869-876 ◽  
Author(s):  
Norisuke H Ata ◽  
Paul A. Glguère
Keyword(s):  
Hydrogen Peroxide ◽  
Water Vapor ◽  
Electric Discharge ◽  
Hydrogen Gas ◽  
Reaction Products ◽  
Hydrogen Atoms ◽  
Eutectic Melting ◽  
Electrodeless Discharge ◽  
Liquid Nitrogen Trap ◽  
Unidentified Species

Hydrogen gas partly dissociated in an electrodeless discharge was mixed downstream with hydrogen peroxide vapor at low pressure (0.1 mm Hg) in a liquid nitrogen trap. The reaction products condensed readily on the wall as a clear, yellowish glass resembling that from dissociated water vapor and other related systems. A manometric study of the warming-up process has revealed four distinct steps. The first two, in which only traces of gas are given off, look like the recombination of trapped free radicals. The major evolution of oxygen upon crystallization of the glassy deposit at 160 °K is ascribed to the decomposition of hydrogen peroxide under the influence of some unidentified species generated in the electric discharge through hydrogen. Experimental evidence for this is presented. In any case the stoichiometry cannot be reconciled with the formation of a metastable intermediate, such as the hypothetical polyoxide H2O4.In the last step beginning around 215 °K more peroxide is decomposed during the eutectic melting of the solid. Qualitatively these phenomena are similar to those shown by the condensate from dissociated water vapor.

The Radiolysis of Water Vapor at Very High Dose Rates. II. Isotope Effects in the Hydrogen Yield from H2O–D2O Mixtures

1973 ◽  
Vol 51 (24) ◽  
pp. 4056-4061 ◽  
Author(s):  
A. W. Boyd ◽  
C. Willis ◽  
O. A. Miller
Keyword(s):  
Water Vapor ◽  
Isotope Effect ◽  
Isotope Effects ◽  
High Dose ◽  
Hydrogen Yield ◽  
Hydrogen Atoms ◽  
Dose Rates ◽  
Very High

The isotope effect in the formation of hydrogen has been measured for H2O–D2O mixtures (10–90% H2O, 0.5–1.0 mg ml−1, 412–138 °C) with and without 1 mol% SF6 at 2 × 1027 eV g−1 s−1. The values of α ((H/D) radiolytic hydrogen/(H/D) H2O–D2O) for the reactions of hydrogen atoms are in the range 3–6 varying with H/D ratio of the substrate. Consideration of possible mechanisms for these large α values leads to the conclusions that reaction of the hydrogen atoms to form hydrogen involves the substrate and that the species H3O may be formed as an intermediate.

Electron spin resonance studies of radicals condensed from irradiated water vapor: reactions of the radicals

1969 ◽  
Vol 47 (12) ◽  
pp. 2149-2154 ◽  
Author(s):  
P. Wardman ◽  
W. A. Seddon
Keyword(s):  
Electron Spin Resonance ◽  
Water Vapor ◽  
Electron Spin ◽  
Radical Scavengers ◽  
Hydrogen Atoms ◽  
Flow Rates ◽  
Spectroscopic Assignment ◽  
Spin Resonance ◽  
Polycrystalline Ice ◽  
Chemical Evidence

Electrons and hydroperoxyl radicals are trapped in polycrystalline ice after irradiation of water vapor and rapid condensation to 77 °K. Using higher sample flow rates than in the earlier work of Seddon, Smith, and Bindner, the electron spin resonance spectra of the trapped electrons (et−) were obtained in both H2O and D2O ice with negligible interference from the underlying HO2• (DO2•) radicals. Addition of C(NO2)4, H2O2, (CH3)2SO, and O2 as radical scavengers confirmed the earlier prediction that reactions with the radicals do not occur in the vapor phase in this system. The results with C(NO2)4 and H2O2 also provided chemical evidence consistent with the spectroscopic assignment for HO2• (DO2•) radicals. Experiments with added isobutylene suggested that hydrogen atoms are formed (possibly in a post-irradiation reaction during condensation) and are also produced on photobleaching et− at 77 °K.

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