Measurement of Rate Constants of Elementary Gas Reactions of Importance to Upper Atmosphere and Combustion Systems

1980 ◽  
Author(s):  
Frederick Kaufman
Keyword(s):  
Rate Constants ◽  
Upper Atmosphere ◽  
Gas Reactions ◽  
Combustion Systems

Null Variance Altitudes for the photolysis rate constants of species with barometric distribution: Illustration on Titan upper atmosphere modeling

Icarus ◽  
2012 ◽  
Vol 218 (2) ◽  
pp. 950-955 ◽  
Author(s):  
Zhe Peng ◽  
Fabien Cailliez ◽  
Michel Dobrijevic ◽  
Pascal Pernot
Keyword(s):  
Rate Constants ◽  
Upper Atmosphere ◽  
Photolysis Rate ◽  
Barometric Distribution

Photodissociation Rate Constants for VUV Processes of CF3Cl and CF2Cl2in the Upper Atmosphere. A MQDO Study

2004 ◽  
Vol 108 (26) ◽  
pp. 5699-5703 ◽  
Author(s):  
E. Mayor ◽  
A. M. Velasco ◽  
I. Martín
Keyword(s):  
Rate Constants ◽  
Upper Atmosphere

Collisional quenching of O 2 ( 1 Δ g )

1969 ◽  
Vol 314 (1516) ◽  
pp. 111-127 ◽  
Keyword(s):  
Rate Constant ◽  
Rate Constants ◽  
Upper Atmosphere ◽  
Private Communication ◽  
Collisional Quenching ◽  
Discharge Flow ◽  
Dry Air ◽  
Recent Estimate

The paper reports determinations of rate constants for the physical deactivation of O 2 ( 1 Δ g ) by gases present in the atmosphere. A modified discharge-flow technique was employed, and relative concentrations of O 2 ( 1 Δ g ) were measured by a photoionization method. The rate constants for the process O 2 ( 1 Δ g ) ) + M → O 2 + M (1) were ≤1.1 x 10 -19 , ≤ 2.1 x 10 -19 , ~2.4 x 10 -18 , ~3.9 x 10 -18 , ~ 1.5 x 10 -17 (cm 3 molecule -1 s -1 ) for M = N 2 , Ar, O 2 , CO 2 , H 2 O respectively. The rate constant for quenching by dry air was measured directly to be 4.3 ± 0.7 x 10 -19 cm 3 molecule -1 s -1 ; this value is consistent with the most recent estimate based on [O 2 ( 1 Δ g )] in the upper atmosphere (3.5 ±1.0 x 10 -19 cm 3 molecule -1 s -1 ; W. F. J. Evans, private communication). Wall deactivation efficiencies varied from 1.2 x 10 -5 to 2.3 x 10 -5 .

In situ REM imaging of surface processes on ceramic bulk crystals from 300 to 1670 K in a conventional TEM

1991 ◽  
Vol 49 ◽  
pp. 660-661
Author(s):  
Z. L. Wang ◽  
J. Bentley
Keyword(s):  
High Temperatures ◽  
Image Resolution ◽  
Atomic Processes ◽  
Crystal Surfaces ◽  
Beam Radiation ◽  
Surface Areas ◽  
Transmission Electron ◽  
Reflection Electron Microscopy ◽  
Gas Reactions

Studying the behavior of surfaces at high temperatures is of great importance for understanding the properties of ceramics and associated surface-gas reactions. Atomic processes occurring on bulk crystal surfaces at high temperatures can be recorded by reflection electron microscopy (REM) in a conventional transmission electron microscope (TEM) with relatively high resolution, because REM is especially sensitive to atomic-height steps.Improved REM image resolution with a FEG: Cleaved surfaces of a-alumina (012) exhibit atomic flatness with steps of height about 5 Å, determined by reference to a screw (or near screw) dislocation with a presumed Burgers vector of b = (1/3)<012> (see Fig. 1). Steps of heights less than about 0.8 Å can be clearly resolved only with a field emission gun (FEG) (Fig. 2). The small steps are formed by the surface oscillating between the closely packed O and Al stacking layers. The bands of dark contrast (Fig. 2b) are the result of beam radiation damage to surface areas initially terminated with O ions.

Residual Gas Reactions in the Electron Microscope: I. Qualitative Observations on the Water Gas Reaction

1968 ◽  
Vol 26 ◽  
pp. 292-293
Author(s):  
Richard E. Hartman ◽  
Roberta S. Hartman ◽  
Peter L. Ramos
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
Gas Phase ◽  
Absolute Temperature ◽  
Residual Gas ◽  
Gas Reactions ◽  
Image Position ◽  
The Right ◽  
Water Gas ◽  
Thinning Rate

The action of water and the electron beam on organic specimens in the electron microscope results in the removal of oxidizable material (primarily hydrogen and carbon) by reactions similar to the water gas reaction .which has the form:The energy required to force the reaction to the right is supplied by the interaction of the electron beam with the specimen.The mass of water striking the specimen is given by:where u = gH2O/cm2 sec, PH2O = partial pressure of water in Torr, & T = absolute temperature of the gas phase. If it is assumed that mass is removed from the specimen by a reaction approximated by (1) and that the specimen is uniformly thinned by the reaction, then the thinning rate in A/ min iswhere x = thickness of the specimen in A, t = time in minutes, & E = efficiency (the fraction of the water striking the specimen which reacts with it).

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