The rate constant (kl) of the reaction OH(v=o) + O3 yields HO2 + O2 measured over the temperature range 220 to 450 K at total pressures between 2 and 5 torr using ultraviolet fluorescent scattering for the detection of OH radicals. An Arrhenius expression was obtained, and the rate constant for the reaction HO2 + O3 yields OH + 2O2 was inferred to be less than 0.1 kl over the entire temperature interval

Anderson, J. G.

Kaufman, F.

English

NASA Technical Reports Server

7 3 - 18152
SPACE RESEARCH COORDINATION CENTER
KINETICS OF THE REACTION
BY
CASE FILE
COPY
JAMES G. ANDERSON AND FREDERICK KAUFMAN
SPONSORED BY
ADVANCED RESEARCH PROJECTS AGENCY
ARPA ORDER NO. 826
SRCC REPORT NO. 183
APPROVED FOR PUBLIC RELEASE
DISTRIBUTION UNLIMITED
UNIVERSITY OF PITTSBURGH
PITTSBURGH, PENNSYLVANIA
FEBRUARY 1973
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SHOULD NOT BE INTERPRETED AS NECESSARILY REPRESENTING THE OFFICIAL POLICIES. EITHER
EXPRESSED OR IMPLIED, OF THE ADVANCED RESEARCH PROJECTS AGENCY OR THE U.S.
GOVERNMENT.
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Unclassified
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-DOCUMENT CONTROL DATA - R & D
(Security fletsillcalion of title, body ol abstract and indexing annotation mu.il be eilored whor, th« overall teporl It cletillled)
I. ORIGINATING A C T I V I T Y (Corporate author)
University of Pittsburgh
Pittsburgh, PA 15213
24. REPOR r SECURITY CLASSIFICATION
Unclassified
2*>. CROUP
J. REPORT TITLE
Kinetics of the Reaction QH(v=o) + 0,
•• " O
4. DESCRIPTIVE NOTES (Type ol toporl and Inclusive dales) '• •
Scientific paper - issued January•.1973:
8- A U T H O R ( S ) (pint name, middle Initial, tmtt name) . ." ' • .
James G. Anderson and' Frederick.Kaufman
«. REPORT DATE .
January 1973
6». C O N T R A C T OR GRANT NO.
DA-31-124-ARO-D-440 x
 :
6. PROJECT NO.
«.
A ' • . ' . ' '
7«. TOTAL NO. OF PAtES • 76. NO. OF RCFS
12 12
9a. ORIGINATOR'S REPORT NUMBER)8>
9b. OTHER HEPOR T'NOISI (Ar.y ol/iar nuaifiort l/i*l mty b tttlfned
Ittlt report) ' ' _ • . .
 f ' . .
tO. DISTRIBUTION STATEMENT
Approved for public release; distribution unlimited.
,,. SUPPLEMENTARY NOTES Qy .
U. S. Army Research Office-Durham
12. SPONSORING MILITARY ACTIV ITY
Advanced Research Projects Agen
1400 Wilson Blvd. ;
Arlington, Va.'; 22209 ;.
N -I 1 •' '' ' ' , :
The rate constant of the reaction OH(v=o) + 0, + H0~.+ 0, was
J -.' ; ' '.G • \£
measured over the temperature range from 220 to 450°K :at 'total pressures
between 2 and, 5 torr using ultraviolet fluorescent scattering:for the detection
of OH radicals. An Arrhenlus expression, k, = 1.3 x 10"12
 e"
1900/RT
 cm3/sec
, ' ^
was obtained and the rate constant for the reaction HQ9 + 0, ->2 OH + 200 was
•
 :
 • 2
inferred to be less than 6.1 ^ over the entire temperature interval.:; ^
POfiM
I MOV <
I f /J "TO ABPLACBB DO KOMM I47>. I JAN *4.
4*1^9 / O OBSOLKTK rON AMMV Ui«.
WHICH 18
Unclassified
Security Classification
ty Clarification
14
K«V »onoe
Hydroxyl
Kinetics
Ozone
Resonance Fluorescence
Flow System
LINK *
HOLE
'
t»T
LINK 0
noun WT
LINK C
Roua • «»T
-
Unclassified
KINETICS,-OF THE REACTION
OH;(v=o) + 0 + H0 + 0
(Submitted to Chemical Physics Letters)
J..6. Anderson
Department,of Physics
and
F. Kaufman
Department of Chemistry
University of 'Pittsburgh
Pittsburgh, Pennsylvania 15213;
January 1973
KINETICS OF THE REACTION
OH (v=o) + 03 + H02 + 02
James G. Anderson
Department of Physics
and
Frederick Kaufman
Department of Chemistry
University of Pittsburgh
Pittsburgh, Pennsylvania 15213
ABSTRACT
k.
The rate constant of the reaction OH (v=o) + 03 •*• H02 + 02 was.
measured over the temperature range from 220 to 450°K at total pressures between
2 and 5 torr using ultraviolet fluorescent scattering for the detection of
OH radicals. An Arrhenius expression,.k-, = 1.3 x 10"12 e'1900/RT cm3/sec
k2
was obtained and the rate constant for the reaction H02 + 03 -> OH + 202 was
inferred to be less than 0.1 k, over the entire temperature interval.
Kinetics of the Reaction*
OH(v=o) + 03 -»• H02 + 02
Technical Report
James G. Anderson
Department of Physics
University of Pittsburgh
Pittsburgh, Pa. 15213
Frederick Kaufman
Department of Chemistry
University of Pittsburgh
Pittsburgh, Pa. 15213
January 1973
U. S. Army Research Office-Durham
Sponsored by
Advanced Research Projects Agency
~ i ARPA Order No. 826
and
The National Science Foundation
Washington, D. C.
Contract No. DA-31-124-ARO-D-440
and
NSF Grant No. GA 27638
Approved for public release;
distribution unlimited
University of Pittsburgh
Pittsburgh, Pa. 15213
The views and conclusions contained in this document are those of the authors
and should not be interpreted as necessarily representing the official policies:
either expressed or implied, of the Advanced Research Projects Agency or the
U. S. Government.
(I) INTRODUCTION .
Bates and Nlcdlet introduced the subject of atmospheric water vapor photo-
chemistry in a classic paper1 more than twenty years ago. A basic step in the
chain mechanism proposed in that paper and in later studies2"5 is the reaction
OH + 03 4. H02
Recently, intense interest in those steps which control the ozone concentration in
the stratosphere5"8 has developed out of a concern for possible photochemical
effects resulting from the deposition of combustion products at stratospheric
levels, principally from high altitude aircraft flights.
Measurement of the hydroxyl-ozone reaction rate constant, ki, has to date
eluded observation. Kaufman9 recommended an upper limit of 5 j* 10"13 cm3/sec '
which has often been quoted as a measured rate constant and used as such in model
calculations. Langley and McSrath10 inferred an upper limit of 10"1'6 cm3/sec
from observing the effects of water vapor on the decay of ozone following the
flash photolysis of an Ar-03-H20 mixture. For a comprehensive review of data
pertaining to ki, see; Hampson et al.11
The previous development of molecular resonance fluorescence as a method
for detecting OH radicals12 has provided the required sensitivity to directly
observe the first order decay of ground state OH in the presence of 0.,. A fast
flow reactor tube operating in the 2 to 5 torr pressure range;was used in this
study to determine kj over the temperature range 220°K ^ . T <. 450°K;
The views and conclusions contained in this document are those of the authors
and should not be interpreted as necessarily representing the official policies,
either expressed or implied, of the Advanced Research Projects Agency or the
U. S. Government.
(II) EXPERIMENTAL
The pyrex flow tube 1 meter in length and 2.5 cm in diameter, coupled
with a fixed position quartz fluorescence cell, used in this study, was identical
to the system previously described.12
Hydroxyl radicals were formed in the reaction
H + N02 -> OH + NO
by the-addition of NOg through a fixed loop injector at the upstream end of the
main flow tube to H atoms formed jn a microwave discharge of H^ and He (see
Figure 1).
Detection of OH was accomplished by observing photons resonantly scattered
at 3090A* (A2£ -> X2n (0-0)) in a direction perpendicular to a collimated beam of
resonance radiation from an H20-Ar discharge lamp which was aligned so as to
illuminate the center of the fluorescence cell.
A 0.3 cm o.d. polished stainless steel movable injector tube, concentric with
the main flow tube, was used to add ozone at any desired point upstream of the
fluorescence cell. Stable temperature control over the range 220° <L T <. 450°K
was achieved using a hollow copper cooling jacket surrounded by a heating mantle,
both of which extend over the full length of;the main flow tube.
The apparatus for the production, handling-and measurement of ozone is
also, displayed in Figure 1. A cold trap containing 500 grams of silica gel
(Davidson, 6-12 mesh), immersed in an isopropanol-dry ice bath at -78°C, was used
to selectively adsorb ozone from a 4 percent 03 to .02 mixture taken directly from
a Welsbach ozonizer (Model T-408).. .A second isoprop.anol immersion bath maintained
at some higher temperature (e.g. -55°C) could be inserted in place of the dry ice
bath. Argon diluent, the flow of which was monitored by a capillary flow meter,
was passed through the trap in order to elute 03- The 03 concentration was
determined by absorption photometry at a point immediately before the argon-
ozone mixture passed into the sliding injector using a quartz cell, a mercury
discharge lamp (Oriel Model 13-61) coupled with a 2540A filter (Baird-Atomic)
and a photomultiplier (RCA 1P28). The total pressure in the quartz absorp-
tion cell, typically 40 torr, was measured with a pressure transducer (Validyne,
Model DP7).
(Ill) PROCEDURE
Hydroxyl radicals were produced by adding NOo in slight excess through
the fixed loop injector to atomic hydrogen as described previously.12 Since
that report, the first order wall decay constant has been reduced from
40 ± 5 sec'1 to 15 ± 3 sec'1 by aging the phosphoric acid wall coating at elevated
temperatures (~440°K). This allows a reduction in the flow velocity for kinetic
experiments.
The flow rates of reactants added to the system were such that the
concentration of OH (^. 3 x 1011 cm1"3) in the reaction zone was three orders of
magnitude smaller than that of the injected 03 concentration (1 - 6 x lO14 cm"3)
which in turn was nearly three orders of magnitude smaller than the carrier gas
concentration (2 x 1017 cm"3). The 0^ mole fraction in the injector was about 0.2.
so that the flow entering through the sliding injector was normally less than one
percent of the total flow. The ozone handling system was arranged such that a
constant flow of argon could enter the sliding injector by either of two routes:
(a) through the silica gel trap containing the adsorbed 0^ or (b) through a by-
pass loop. Therefore, changes in the OH concentration at the fluorescence cell'
as a,function of injector position with: (a) a measured mole fraction of argon-
ozone or.(b) pure argon added through the injector, constitute the fundamental
experimental data.
In order to verify that no ozone was lost in the injector assembly, the
OH resonance lamp was replaced by a mercury discharge lamp and an 03 absorption
experiment was performed in the fluorescence cell at the downstream end of the
flow tube. The 0, concentrations measured at the two locations agreed within
the experimental uncertainty (±10 percent).
(IV) RESULTS
Figure 2 presents a typical example of the OH decay as a function of
injector position for two cases, one with argon alone added through the injector
and another with an ozone-argon ratio of 1:5. The negligible effect of the
injector and of added Ar on the OH decay is apparent, as is the linearity of the
logarithmic decay of OH concentration over an order of magnitude in the .presence
of 0.,, verifying the pseudo-first order nature of the removal process.
The first order rate constant calculated from the OH decay plots was
found to be independent of total pressure in the range of study (2 to 5 torr),
independent of the N02 excess flow through the loop injector, and exactly
proportional to the 0., concentration within the experimental uncertainty of the
0« concentration measurement. At 297°K the bimolecular rate constant was
found to be 5.5 ± 1.5 x IQ'11* cm3/sec.
The possibility of OH regeneration by the reaction
H02 + 03 | OH + 2Q2
was considered; Hydroxy.Tdecay profiles encompassing the range 0 < k :/k2 < °°
were calculated"and compared with the observed decay profiles. As the'ratio
k!/k2 becomes less than about ten, distinct curvature in the logarithmic;decay
plots of'OH results, which is clearly inconsistent with the observations. It
can thus be inferred that k2 <. 5 x 10~15 cm3/sec. ,
Preliminary results over the temperature range 220 to 450°K, presented
in Figure.3, indicate an activation energy of 1.9 kcal/mole and lead to the
Arrhenius expression ^ = 1.3 x 10~12 exp(-1900/RT) cm3 sec'1.
The room,temperature reaction rate constant k± = 5.5 ±1 .5 x 10"14 cm3/sec
is in strong disagreement with the upper limit of 10~16 .cm3 /sec reported by
Langley and McGrath10 from flash photolysis studies. We suggest that the reaction
OH ••+ OH -> HpO + 0, which was, not taken into account in their analysis, greatly
decreases the OH concentration in their experiments and makes it impossible to
set .limits for k.
REFERENCES
*This research was supported in part by the National Science Foundation,
Atmospheric Sciences Division (Aeronomy) under Grant No. GA 27638 and by the
Advanced Research Projects Agency, The Department of Defense, and was monitored
by U. S. Army Research Office-Durham, Box CM, Duke Station, Durham, N. C. 27706,
under Contract No. DA-31-124-ARO-D-440.
I, R. D. Bates and M. Nicolet, J. Geophys, Res. 55., 301 (1950).
2. B. G. Hunt, J. Geophys. Res., 7]_, 1385 (1966).
3. J. Hampson, T.N. 1627/64, Canadian Armament'Research Development Establish-
ment, 1964.
4. C. B. Leovy, J. Geophys. Res., 7±, 417 (1969).
5. E. Hesstvedt, Geof. Publik n27.
6. H. S. Johnston, Science 173_, 517 (1971).
7. P. 0. Crutzen, Quart. J. Roy. Meteorol. Soc. 96_, 320 (1970).
8. M. Nicolet, Planet. Space Sci., 20, 1671 (1972).
9. F. Kaufman, Ann.de Geophys., 20_, 106 (1964).
10. K. R. Langley and W. D. McGrath, Planet. Space Sci., 19_, 413 (1971.).
II. N. B. S. Report 10828 April, 1972.
12. J. G. Anderson and F. Kaufman, Chem. Phys. Letters, 16, 375 (1972).
LIST OF FIGURE CAPTIONS
Figure 1. Schematic description of the ozone system, main reaction tube,
fluorescence cell and resonance lamp.
Figure 2. Hydroxyl decay resulting from the addition of pure argon and an
argon-ozone mixture through the sliding probe.
Figure 3. Arrhenius plot of k,(T) versus 1/T from 220 to 450°K.
I
o
<
bJ
3s
N
5
o
Ar Added Through
Injector
03 + Ar "Added
Through Injector
2O 40 60 80
Injector Tip To Fluorescence Cell Distance (cm)
iP»O
T T
Temperature Dependence
of
= 1.9 kca|/m
10007 T(°K)


Kinetics of the reaction OH (v equals 0) plus O3 yields HO2 plus O2

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