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Kinetic studies of O(¹S) formation from atomic oxygen recombination Wassell, Peter Thomas
Abstract
The molecular and atomic dependencies of the O(¹S) emission have been studied in the laboratory by generating oxygen atoms in a discharge flow system. The intensity of the emission is found to have the dependence [See thesis for equation] where M is the total particle concentration in the system. From absolute measurements of the O(¹S) atomic line, the overall rate constant k[sub T] is found to be equal to 2.7 ± 0.3 x 10⁻²⁷cm⁶s⁻¹ at 300K. The observed dependence is shown to be inconsistent with the proposed Chapman mechanism for the excitation of O(¹S) [See thesis for equation] (1) However the observations are found to be in agreement with a "Barth-type" mechanism, where a metastable oxygen molecule (O₂*) is formed in the recombination of two oxygen atoms in the presence of a third body, [See thesis for equation] (2) followed by energy transfer to a third oxygen atom to form O(¹S) [See thesis for equation] (3) and the radiative emission of O(¹S) at 557.7 nm. The possible electronic states of O₂ corresponding to O₂* are dis-cussed. Although the identity of the O₂* remains to be found, the major loss process of this intermediate is found to be quenching by atomic oxygen in [See thesis for equation] (4) rather than by molecular oxygen or argon [See thesis for equation] quenched products (5) [See thesis for equation] quenched products (6) Until recently the major quencher of O(¹S) was thought to be the ground-state oxygen atom [See thesis for equation] quenched products (7) However, in this system, the dependence of the 557.7 nm emission found to be consistent with the predominate quenching of O(¹S) by O₂(a¹Δg): [See thesis for equation] quenched products (8) The rate constant k₈ is estimated to be 7 ± 3 x 10⁻¹⁰cm³ s⁻¹ by comparison for quenching of O(¹S) by O₂. [See thesis for equation] quenched products (9) O₂(a¹Δg) is expected to be present in all laboratory systems involving atomic oxygen due to its formation by either heterogeneous or homogeneous recombination of O[³P]. Due to the magnitude of k₈, O₂(a¹Δg) is expected to be the major quencher of O(¹S) in most of these systems. Using currently accepted values for the concentration of O₂(a¹Δg) in the terrestrial nightglow layer, the quenching of O(¹S) by O₂(a¹Δg) is found to be unimportant in this region compared to its radiative decay. Other atmospheric implications of this investigation's results are discussed.
Item Metadata
Title |
Kinetic studies of O(¹S) formation from atomic oxygen recombination
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
1981
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Description |
The molecular and atomic dependencies of the O(¹S) emission have been studied in the laboratory by generating oxygen atoms in a discharge flow system. The intensity of the emission is found to have the dependence
[See thesis for equation]
where M is the total particle concentration in the system.
From absolute measurements of the O(¹S) atomic line, the overall rate constant k[sub T] is found to be equal to 2.7 ± 0.3 x 10⁻²⁷cm⁶s⁻¹ at 300K.
The observed dependence is shown to be inconsistent with the proposed Chapman mechanism for the excitation of O(¹S)
[See thesis for equation] (1)
However the observations are found to be in agreement with a
"Barth-type" mechanism, where a metastable oxygen molecule (O₂*) is formed in the recombination of two oxygen atoms in the presence of a third body,
[See thesis for equation] (2)
followed by energy transfer to a third oxygen atom to form O(¹S)
[See thesis for equation] (3)
and the radiative emission of O(¹S) at 557.7 nm.
The possible electronic states of O₂ corresponding to O₂* are dis-cussed. Although the identity of the O₂* remains to be found, the major loss process of this intermediate is found to be quenching by atomic oxygen in
[See thesis for equation] (4)
rather than by molecular oxygen or argon
[See thesis for equation] quenched products (5)
[See thesis for equation] quenched products (6)
Until recently the major quencher of O(¹S) was thought to be the ground-state oxygen atom
[See thesis for equation] quenched products (7)
However, in this system, the dependence of the 557.7 nm emission found to be consistent with the predominate quenching of O(¹S) by O₂(a¹Δg):
[See thesis for equation] quenched products (8)
The rate constant k₈ is estimated to be 7 ± 3 x 10⁻¹⁰cm³ s⁻¹ by comparison for quenching of O(¹S) by O₂.
[See thesis for equation] quenched products (9)
O₂(a¹Δg) is expected to be present in all laboratory systems
involving atomic oxygen due to its formation by either heterogeneous
or homogeneous recombination of O[³P]. Due to the magnitude of k₈, O₂(a¹Δg) is expected to be the major quencher of O(¹S) in most of these systems.
Using currently accepted values for the concentration of O₂(a¹Δg) in the terrestrial nightglow layer, the quenching of O(¹S) by O₂(a¹Δg) is found to be unimportant in this region compared to its radiative decay. Other atmospheric implications of this investigation's
results are discussed.
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Genre | |
Type | |
Language |
eng
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Date Available |
2010-03-29
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Provider |
Vancouver : University of British Columbia Library
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Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
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DOI |
10.14288/1.0060743
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Campus | |
Scholarly Level |
Graduate
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Aggregated Source Repository |
DSpace
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For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.