Kinetics of ClONO2Reactive Uptake on Ice Surfaces at Temperatures of the Upper Troposphere

2005 ◽  
Vol 109 (44) ◽  
pp. 9986-9996 ◽  
Author(s):  
Miguel A. Fernandez ◽  
Robert G. Hynes ◽  
Richard A. Cox
Keyword(s):  
Upper Troposphere ◽  
Ice Surfaces ◽  
Kinetics Of

scholarly journals Different photolysis kinetics at the surface of frozen freshwater vs. frozen salt solutions

2010 ◽  
Vol 10 (22) ◽  
pp. 10917-10922 ◽  
Author(s):  
T. F. Kahan ◽  
N.-O. A. Kwamena ◽  
D. J. Donaldson
Keyword(s):  
Aqueous Solution ◽  
Aqueous Phase ◽  
Salt Solutions ◽  
Ice Surface ◽  
Photolysis Rates ◽  
Quasi Liquid Layer ◽  
Ice Surfaces ◽  
Halide Salts ◽  
Physical And Chemical ◽  
Kinetics Of

Abstract. Reactions at air-ice interfaces can proceed at very different rates than those in aqueous solution, due to the unique disordered region at the ice surface known as the quasi-liquid layer (QLL) . The physical and chemical nature of the surfacial region of ice is greatly affected by solutes such as sodium halide salts. In this work, we studied the effects of sodium chloride and sodium bromide on the photolysis kinetics of harmine, an aromatic organic compound, in aqueous solution and at the surface of frozen salt solutions above the eutectic temperature. In common with other aromatic organic compounds we have studied, harmine photolysis is much faster on ice surfaces than in aqueous solution, but the presence of NaCl or NaBr – which does not affect photolysis kinetics in solution – reduces the photolysis rate on ice. The rate decreases monotonically with increasing salt concentration; at the concentrations found in seawater, harmine photolysis at the surface of frozen salt solutions proceeds at the same rate as in aqueous solution. These results suggest that the brine excluded to the surfaces of frozen salt solutions is a true aqueous solution, and so it may be possible to use aqueous-phase kinetics to predict photolysis rates at sea ice surfaces. This is in marked contrast to the result at the surface of frozen freshwater samples, where reaction kinetics are often not well-described by aqueous-phase processes.

scholarly journals Reaction between CH<sub>3</sub>C(O)OOH (peracetic acid) and OH in the gas phase: a combined experimental and theoretical study of the kinetics and mechanism

2020 ◽  
Vol 20 (21) ◽  
pp. 13541-13555
Author(s):  
Matias Berasategui ◽  
Damien Amedro ◽  
Luc Vereecken ◽  
Jos Lelieveld ◽  
John N. Crowley
Keyword(s):  
Gas Phase ◽  
Peracetic Acid ◽  
Theoretical Study ◽  
Rate Coefficient ◽  
Theoretical Calculations ◽  
Title Reaction ◽  
Upper Troposphere ◽  
Reaction Proceeds ◽  
Kinetics Of ◽  
Good Agreement

Abstract. Peracetic acid (CH3C(O)OOH) is one of the most abundant organic peroxides in the atmosphere; yet the kinetics of its reaction with OH, believed to be the major sink, have only been studied once experimentally. In this work we combine a pulsed-laser photolysis kinetic study of the title reaction with theoretical calculations of the rate coefficient and mechanism. We demonstrate that the rate coefficient is orders of magnitude lower than previously determined, with an experimentally derived upper limit of 4×10-14 cm3 molec.−1 s−1. The relatively low rate coefficient is in good agreement with the theoretical result of 3×10-14 cm3 molec.−1 s−1 at 298 K, increasing to ∼6×10-14 cm3 molec.−1 s−1 in the cold upper troposphere but with associated uncertainty of a factor of 2. The reaction proceeds mainly via abstraction of the peroxidic hydrogen via a relatively weakly bonded and short-lived prereaction complex, in which H abstraction occurs only slowly due to a high barrier and low tunnelling probabilities. Our results imply that the lifetime of CH3C(O)OOH with respect to OH-initiated degradation in the atmosphere is of the order of 1 year (not days as previously believed) and that its major sink in the free and upper troposphere is likely to be photolysis, with deposition important in the boundary layer.

scholarly journals Reaction between CH<sub>3</sub>C(O)OOH (peracetic acid) and OH in the gas-phase: A combined experimental and theoretical study of the kinetics and mechanism

2020 ◽  
Author(s):  
Matias Berasategui ◽  
Damien Amedro ◽  
Luc Vereecken ◽  
Jos Lelieveld ◽  
John N. Crowley
Keyword(s):  
Peracetic Acid ◽  
Rate Coefficient ◽  
Theoretical Calculations ◽  
Upper Troposphere ◽  
Reaction Proceeds ◽  
Reaction Complex ◽  
One Year ◽  
Peroxy Acids ◽  
Kinetics Of ◽  
Good Agreement

Abstract. Peracetic acid (CH3C(O)OOH) is one of the most abundant organic peroxides in the atmosphere, yet the kinetics of its reaction with OH, believed to be the major sink, have been studied only once experimentally. In this work we combine a pulsed-laser photolysis kinetic study of the title reaction with theoretical calculations of the rate coefficient and mechanism. We demonstrate that the rate coefficient is orders of magnitude lower than previously determined, with an experimentally derived upper limit of ≤ 4 × 10−14 cm3 molecule−1 s−1. The relatively low rate coefficient is in good agreement with the theoretical result of 3 × 10−14 cm3 molecule−1 s−1 at 298 K, increasing to ~ 6 × 10−14 in the cold upper troposphere, but with associated uncertainty of a factor-two. The reaction proceeds mainly via abstraction of the peroxidic-hydrogen via a relatively weakly bonded and short-lived pre-reaction complex, in which H-abstraction occurs only slowly due to a high barrier and low tunneling probabilities. Our results imply that the lifetime of CH3C(O)OOH with respect to OH-initiated degradation in the atmosphere is of the order of one year (and not days as previously believed) and that its major sink in the free and upper troposphere is likely to be photolysis, with dry-deposition important in the boundary layer. Similar conclusions can be made for other, saturated peroxy-acids.

Photolysis Kinetics of Toluene, Ethylbenzene, and Xylenes at Ice Surfaces

2016 ◽  
Vol 120 (34) ◽  
pp. 6693-6697 ◽  
Author(s):  
Alexa A. Stathis ◽  
Albanie K. Hendrickson-Stives ◽  
Tara F. Kahan
Keyword(s):  
Ice Surfaces ◽  
Kinetics Of

scholarly journals Reaction kinetics of OH + HNO3 under conditions relevant to the upper troposphere/lower stratosphere

2018 ◽  
Vol 20 (38) ◽  
pp. 24652-24664 ◽  
Author(s):  
Frank A. F. Winiberg ◽  
Carl J. Percival ◽  
Robin Shannon ◽  
M. Anwar H. Khan ◽  
Dudley E. Shallcross ◽  
...  
Keyword(s):  
Reaction Kinetics ◽  
Lower Stratosphere ◽  
Detection Method ◽  
Upper Atmosphere ◽  
Upper Troposphere ◽  
Temperature Range ◽  
Alternative Detection ◽  
Kinetics Of

Key upper atmosphere reaction of HNO3 + OH studied over extended pressure and temperature range using new alternative detection method.

Direct observations of radiation-enhanced transformations in glass

1983 ◽  
Vol 41 ◽  
pp. 354-355
Author(s):  
J. F. DeNatale ◽  
D. G. Howitt
Keyword(s):  
Glass Matrix ◽  
Diffusion Mechanism ◽  
Bubble Formation ◽  
Silicate Glasses ◽  
Phase Decomposition ◽  
Direct Observations ◽  
Thin Foils ◽  
Oxygen Bubble ◽  
Electron Energy Loss ◽  
Kinetics Of

The electron irradiation of silicate glasses containing metal cations produces various types of phase separation and decomposition which includes oxygen bubble formation at intermediate temperatures figure I. The kinetics of bubble formation are too rapid to be accounted for by oxygen diffusion but the behavior is consistent with a cation diffusion mechanism if the amount of oxygen in the bubble is not significantly different from that in the same volume of silicate glass. The formation of oxygen bubbles is often accompanied by precipitation of crystalline phases and/or amorphous phase decomposition in the regions between the bubbles and the detection of differences in oxygen concentration between the bubble and matrix by electron energy loss spectroscopy cannot be discerned (figure 2) even when the bubble occupies the majority of the foil depth.The oxygen bubbles are stable, even in the thin foils, months after irradiation and if van der Waals behavior of the interior gas is assumed an oxygen pressure of about 4000 atmospheres must be sustained for a 100 bubble if the surface tension with the glass matrix is to balance against it at intermediate temperatures.

Irradiation behavior of pyrolytic silicon carbide

1983 ◽  
Vol 41 ◽  
pp. 72-73
Author(s):  
R. J. Lauf
Keyword(s):  
Silicon Carbide ◽  
Fission Products ◽  
Thermodynamics And Kinetics ◽  
Neutron Fluences ◽  
Fuel Particles ◽  
Sic Coatings ◽  
Irradiation Behavior ◽  
Kinetics Of ◽  
Htgr Fuel

Fuel particles for the High-Temperature Gas-Cooled Reactor (HTGR) contain a layer of pyrolytic silicon carbide to act as a miniature pressure vessel and primary fission product barrier. Optimization of the SiC with respect to fuel performance involves four areas of study: (a) characterization of as-deposited SiC coatings; (b) thermodynamics and kinetics of chemical reactions between SiC and fission products; (c) irradiation behavior of SiC in the absence of fission products; and (d) combined effects of irradiation and fission products. This paper reports the behavior of SiC deposited on inert microspheres and irradiated to fast neutron fluences typical of HTGR fuel at end-of-life.

The Ordered Phase Formation in Ti-Al-Ga Alloys

1970 ◽  
Vol 28 ◽  
pp. 440-441
Author(s):  
Shiro Fujishiro ◽  
Harold L. Gegel
Keyword(s):  
Thermal Stability ◽  
High Temperature ◽  
Titanium Alloys ◽  
Growth Kinetics ◽  
Stoichiometric Composition ◽  
Good Potential ◽  
Alpha Titanium ◽  
Cold Rolled ◽  
Kinetics Of ◽  
Thermal Stability Of

Ordered-alpha titanium alloys having a DO19 type structure have good potential for high temperature (600°C) applications, due to the thermal stability of the ordered phase and the inherent resistance to recrystallization of these alloys. Five different Ti-Al-Ga alloys consisting of equal atomic percents of aluminum and gallium solute additions up to the stoichiometric composition, Ti3(Al, Ga), were used to study the growth kinetics of the ordered phase and the nature of its interface.The alloys were homogenized in the beta region in a vacuum of about 5×10-7 torr, furnace cooled; reheated in air to 50°C below the alpha transus for hot working. The alloys were subsequently acid cleaned, annealed in vacuo, and cold rolled to about. 050 inch prior to additional homogenization

Ion Beam Induced Interfacial Reactions in Molybdenum Thin Films on Silicon

1981 ◽  
Vol 39 ◽  
pp. 162-163
Author(s):  
L. J. Chen ◽  
L. S. Hung ◽  
J. W. Mayer
Keyword(s):  
Ion Beam ◽  
Chemical Vapor ◽  
Interfacial Reactions ◽  
Practical Applications ◽  
Microelectronic Devices ◽  
Recent Emergence ◽  
Chemical Vapor Deposited ◽  
Atomic Mixing ◽  
Silicon Interface ◽  
Kinetics Of

When an energetic ion penetrates through an interface between a thin film (of species A) and a substrate (of species B), ion induced atomic mixing may result in an intermixed region (which contains A and B) near the interface. Most ion beam mixing experiments have been directed toward metal-silicon systems, silicide phases are generally obtained, and they are the same as those formed by thermal treatment.Recent emergence of silicide compound as contact material in silicon microelectronic devices is mainly due to the superiority of the silicide-silicon interface in terms of uniformity and thermal stability. It is of great interest to understand the kinetics of the interfacial reactions to provide insights into the nature of ion beam-solid interactions as well as to explore its practical applications in device technology.About 500 Å thick molybdenum was chemical vapor deposited in hydrogen ambient on (001) n-type silicon wafer with substrate temperature maintained at 650-700°C. Samples were supplied by D. M. Brown of General Electric Research & Development Laboratory, Schenectady, NY.

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