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Rate constant measurements for the reaction of Cl atoms with nitric acid over the temperature range 240–300 K
21 January 1983
CHEhflCAL PHYSICS LETTERS
Volume 94, number 3
RATE CONST_ANT MEASUREMENTS
FOR THE REACTION OF Cl ATOMS WITH NITRIC ACID
OVER THE TEMPERATURE
RANGE 240-300
Michael J. KURYLO,
L. MURPHY and Geoffrey
Jennifer
K L. KNABLE
Chemical Kinetics Division. National Bureau of Standards, Washington. DC20234.
USA
Received 6 October 1982
Rate constants for the reaction between Cl atoms and HOh’02 were measured at 243,264. and 198 I( by the flash photolysis resonance fluorescence technique_ The data can be fit to the Arrhenius expression R1 = 5.1 X lo-” esp(- 1700/T) cm3 m01ecule~~ s-’ snd indicate that the reaction is unimportanr in stratospheric Ci atom removal. Sources of measurement error in this and earlier stidues are discussed.
1. Introduction
Hydrogen atom abstraction from both organic and inorganic compounds by chlorine atoms has been a topic of considerable interest in recent years due primarily to the role played by such reactions in stratospheric chemistry. For example, the efficiency of the chlorine catalytic cycle for stratospheric ozone removal [I] is determined in part by the rate at which active chlorine is converted into HCl. In this regard, the reaction of Cl atoms with nitric acid Cl i- HONO-, + HCl + NO3
(1)
has been considered unimportant [2] based on the results of two discharge flow mass spectrometric kinetic studies [3,4] which report room-temperature values fork1 of (6-S 2 3.4) X IO-l5 and < 2 X lo-t7 cm3 molecule-l s-l respectively_ More recently a third research group [5] has reported a room-temperature measurement by flash photolysis resonance absorption from which they calculate k, = (3-4 + 1.6) X IO-14 cm3 molecule-l s-l_ These results raise considerable doubt about the accuracy with which we know k, _ Coupled with recent observations [6-S] on the somewhat anomalous (negative) temperature dependence of the OH + HONO reaction 0H+HONO-,+H30+N03,
(2)
this latest study [5] may be used to suggest a non-negligible role for reaction (1) in removing stratospheric 0 009-2614/S3/0000-0000/o/s
03.00 0 1983 North-Holland
chlorine_ For example, if we accept the Clark et al [S] room-temperature value for lit and an E/R value of -1100 K [of comparable magnirude to the E/R of reaction (2)]. we find that reaction (1) can play a modest role in HCI formation in the midstratosphere relative to Cl + CH, and Cl + HO, [ 1.21. Cl+CH,+HCI+CH,,
(3)
Cl+HO,+HCI+O,_
(4)
The lack of any definitive information from the published studies on reaction (1) with which to either support or reject such speculation prompted us to conduct our own temperature dependence investigation of k, using the flash pliotolysis resonance fluorescence (FPRF) technique_ The results of these experiments at 243,264, and 298 K are reported in this communication_
2. Experimental Complete FPRF procedural details as well as information on the double-walled pyres reactor used in the present work may be found in our recent publication on the OH + HONO, reaction [7] _Chlorine atoms were produced via the flash photolysis of 12-30 mTorr of CCI, (1 mTorr = 0.133 Pa = 9_6SS7 X 1015/T(K) molecules cme3) at wavelengths longer than 165 nm. This range in Ccl, concentration coupled with changes in flash lamp pressure (intensity) permitted variation 281
CHEMICAL PHYSICS LETTERS
Volume 93, number 3
in initial Cl atom concentration, IO 3 x IO” cme3. The absence
[CIJO, from 3 X lOlo of any perceprible dependence of the atom decay rates on initial atom concentrarion was viewed as evidence for the lack of inrcrference from secondary arom-radical reactions in this range of [Cl],. The chlorine atom fluorescence resonantly scattered from rile microwave discharge resonanLy lamp (=O.l% Cl, in lie ai *I Torr) was viewed without wavelength resolution through a BaF, window (A 2 135 nm) using a solar blind photomultiplier and standard pulse caunkg eiecrronics. Fluoreswnce signal accumulated from multiple csperimcnts was stored in a microprocessor based multichannel analyzer system where the decay curves were analyzed assunting pseudo-firstorder kinetic behavior. &action mis~ures consisting of CCI, _HONO? _and either Ar or N, as a diluent gas were prepared manonxrrically in @ass storag bulbs prior to their being Ilowed through the reaction cell (~100 cm3 s-l) at prcssurcs berwecn 15 and 50 Torr. The nitric acid con-
ccntration
during each run was monitored
by optical
sbsorprion
(a = 1.63 X lo-l7 cm2 at iS4.9 nm) 16.9. IO] in a 10 cm ccl1 located on the exit port of the rcac-
IN. The light source for these measurements l’cn-r3?
was a Hg
is&red by a IS5 nm bandpass filter/ 0.25 111 Illo~locllron~ator combination. The reactant 11rw could hc divcrrcd directly inro the absorption hnp
cell.
bypassing the reactor. thereby providing a check on an) major HONO decomposition in the reaction cell. As in our earlier work. these procedures enabled us to monitor nitric acid concentrations with a precision of hc1Icr tlirtn 3 few percent.
21 January 1983
Table 1 Rare constants for the reaction Cl + HONO + HCI + NO3 T UQ
Dtiuent gas (Torr)
x-1 X 10” Standard (cm3 mole- deviation cule-’ s-l)
298
20 _4r, 20 Nz,SO N2
16-7
264
15 N2.20N2.50Nz
143
20N2,50N2
Total uncertainty
%l_O
+2.1 -5.2
8.4
21.0
+1.9 -3.3
4.6
51.4
+2.7 -3.5
cubic” for the first-order
Cl decay rate versus HONO, concentration data and took into account the uncertainties in both these variables [ 1 1] _The data at 29s K used for this analysis are shown in fig. l_ As can be seen we were forced to limit our studies to HONO? partial pressures below Z=100 mTorr due to the severe attenuation (absorption) [12,13] of the fluorescence signal between 135 and 140 nm by nitric acid. This, in turn. prevented us from conducting experiments over a very wide range of first-order decay rates thereby restricting the calculation of k, to runs exhibiting small differences in Cl atom lifetimes. Nevertheless a number of diagnostic tests were conducted to demonstrate that the amount by which our measured decay rates exceeded the diffusional loss rate of Cl was due primarily to the gas phase homogeneous title reaction.
?!itric acid was prepared by va~uu~~~ distilling a mixturn ~fdr?; sodium nitrate and concentrated sulfuric
:IA.
Following
purification
by trap-to-trap
distillation
in KIS srorcd 31 7S Ii until use. Spectrograde CC14 was dcgasscd via several freeze-pllIiip-thaw cycles prior 10 usr‘. Ultra high purity Ar and N, were used directly 1‘rom llic sylindcrs wiliioul further purification_
:i~
I 3. Results
’
and discussion
The results of our measurements at 743. 264? and 2% K arc summarized in table l_ The first column of unccrGlties rspressed for kl are the standard devia-
tiws from iIn itcrativc solution of tltc “least-squares
ris. I_ Plot of fast order decay rates, k. versus HONO concentration at 298 K. Diluent gas pressures: X, 20 Torr AI; o_ 20 Torr N1 ; +. 50 Torr Nz _
One of our first concerns was that signifkant production of OH from photolysis of the nitric acid could initiate secondary chemistry, not by direct reaction with Cl (which is expected to be slow) [14], but rather via rapid generation of NO, which could then react with Cl OH -I-HONO? + H,O -I-N03,
(2)
Cl+N03-+C10+N0,_
(5)
Indeed. modeling calculations showed that for initial concentrations of Cl and OH typical of our experiments. the apparent X-t value could increase signifkantly above 7 X 1O-‘5 for X-5 = I X 1 O--l1 cm3 molecule-*
s-I_ However, this result proved to be extremely sensitive to variations in [Cl]0 and [OH]0 in the IOtt cr1r3
region such that our experimental
variations in
flash
intensity should have yielded vastly differing first order decay raten We are therefore able to conclude generally that such secondary processes were insignificant in our experiments and more specific+ that k5 is substantially smaller than 1O-*l cm3 molecule-t s-t (the ritte constant [3] for the 0 + NO3 reaction). A second potential source of error in our measure-
ments was the contribution decays of the reaction
21 January 1983
CHEMICAL PHYSICS LElTERS
Volume 94, number 3
to the observed Cl atom
Cl + NO, + hl --f CINOz + hl,
(6)
where NO, could be present as an impurity in the nitric acid. There is no doubt that some of the fluctuations in our decay rate data are due to trace NO-, impurities or to NO, arising from HONO, decompisition. When extreme care was taken to thoroughly clean and bake out under vacuum all storage bulbs, the rcaclion cell. and its ancillary tubing such scatter was minimized and reasonably reproducible data could be obtained_ If one were to attribute the difference between our 30 Torr room-temperature data and the fit value of ref. [3] as being due to trace amounts of NO2 in our experiments, it would require a near constant NO, impurity level of 0.94%. This is in marked contrast to the 0.2-0.3% upper limit set from both analytical and kinetic considerations in our OH + HONO, study. Furthermore such an impurity level would have caused our measured decay rates to increase by nearly 80% in changing diluent gas pressure from 20 to.50 Torr_ As can be seen in fig. 1, our 20 Torr Ar, 20 Torr N2 1and
50 Torr N, data do not differ significantly in any statistically meaningful manner. A similar attempt at quantifying the difference between our work and that of ref. [4] leads to even more profound contradictions. The absence of a measurable pressure effect in our room-temperature data is itself consistent with the aforementioned OJ-03% upper limit on NO, since the latter would correspond to a change in slope in fig. 1 of 10 s-1 per lo0 mTorr HONO?. This in turn translates into a potential systematic overestimation of X-1at 29s K of 3.1 X 10-l” cm3 molecule-is-t. Thus if we take an extremely conservative approach and add this uncertainty to twice the statistical error we obtain Ii,(39SK)=(16_7+z:$X
IO-l5
cn~~n~olecule-ls-~.
Similar analysis can be performed for the 264 and 243 K data as well. These experiments were typified by much better reproducibility (less scatter) than the 298 K data suggesting that some slight decomposition of HONO occurring in the reaction cell at room temperature was minimized at the lower trmper~turcs. Thus we can place a more restrictive estimate on any systematic error in RI due to reaction (6) at these temFratures leading to the final column of uncertainties in table 1. It should be noted that despite the better reproducibility of the lower temperature data, the statistical uncertainties are greater than at 298 K due to the far greater number of experiments which were conducted at that temperature_ The three k, values are plotted in Arrhcnius form in fig.2 with the error bars of the final column of table 1 _
Fig_ 2. Arrhenius plot of X-i values from the presenr work. Solid line is I lean-squ;rrcs fir. Error bars xc csphincd in ihc test.
CHEhlICAL
PHYSICS
21 January
LETTERS
The compatibility
1983
of our data with an Arrhenius es-
pression characterized by a positive E/R of 1700 K strongly supports the original position [2] that the reaction of Cl atoms with nitric acid does not contribute appreciably to Cl atom removal in the midstratosphere. Similarly it has even less of an effect on the calculated nitric acid flux.
Acknowledgement
This work was supported bon
I’rogmrn
of the
Chenlical
in part by the FluorocafManufacturers
Associa-
and the Upper Atmospheric Research Program of the National Aeronautics and Space Administration tion
References .I 1 I- R.D. Iludson.
editor-incbicf, WhlO Global Ozone Rcstarch and hlonitoring Project. Report No. I I, The Str~tospbrrc 1961: Theory and hlcasurements. [ 21 \\‘.I& Dchlorc. R.T. Wason. D.hl. Golden. R-1:. Ilampson. h1.J. Kurylo. C.J. llowlrd. M.J. hlolina and A.R. Ravishankara. Clwmical Eimics and Iahotochcniic~l Lktn for Use in Stratospbcric hlodcling. J.P.L. Publintion 82-57 (15 July 1961). 131 hl.-T. Lcu aud W.B. Dc>lorc. Cbcm. Pbys. Lcttcrs 41 (1976) 1’1. J. Cbem. Pbys. I41 G. I’oulc~. C. LeIIrasand J. Combouricu, 69 (1978) 767. I-‘1 K.11. Clark, D. llumin and J.Y. Jezcqucl. J. Photocbem. 18 (1982) 39. N.hl. Krcultcr, R.C. Shah. 161 P.11. Wine, A.R. Rwislnnkarii, JAI. Nicovich, Geophys.
R.L. Thompson
and D.J. Wuebblcs,
J.
Rcs. 86 (198 1) I 105.
I71 hl.J. Kurylo.
llcs. 67 (1982)
IS1 J -1. hlargitan
K-1). Cornctt and J.L. Murphy. J. Ceophys. 3081. and R.T. Watson. J. Phys. Cbcm.. lo bc
published. 191 l-‘. Binume. J. I’hotochem. I! (1973) 139. 1101 11-N. N&on. WJ. hlxinelli and H.S. Johnston, Chem. Phys. Letters 78 (1961) 495. 1111 D. York. fin. J. Phys.44 (1966) 1079. and K_P. Wayne, J. Photo1131 GS. Ueddard. D-J. Cixbxdi them. 3 (1974175) 321. 1131 II. Okabc. J. Chcm. Phys. 72 (1980) 6642. and the StratoI141 R.D. Hudson, cd., Cblorofluoromethancs sphere. NASA RP IO IO (August 1977).
CHEhflCAL PHYSICS LETTERS
Volume 94, number 3
RATE CONST_ANT MEASUREMENTS
FOR THE REACTION OF Cl ATOMS WITH NITRIC ACID
OVER THE TEMPERATURE
RANGE 240-300
Michael J. KURYLO,
L. MURPHY and Geoffrey
Jennifer
K L. KNABLE
Chemical Kinetics Division. National Bureau of Standards, Washington. DC20234.
USA
Received 6 October 1982
Rate constants for the reaction between Cl atoms and HOh’02 were measured at 243,264. and 198 I( by the flash photolysis resonance fluorescence technique_ The data can be fit to the Arrhenius expression R1 = 5.1 X lo-” esp(- 1700/T) cm3 m01ecule~~ s-’ snd indicate that the reaction is unimportanr in stratospheric Ci atom removal. Sources of measurement error in this and earlier stidues are discussed.
1. Introduction
Hydrogen atom abstraction from both organic and inorganic compounds by chlorine atoms has been a topic of considerable interest in recent years due primarily to the role played by such reactions in stratospheric chemistry. For example, the efficiency of the chlorine catalytic cycle for stratospheric ozone removal [I] is determined in part by the rate at which active chlorine is converted into HCl. In this regard, the reaction of Cl atoms with nitric acid Cl i- HONO-, + HCl + NO3
(1)
has been considered unimportant [2] based on the results of two discharge flow mass spectrometric kinetic studies [3,4] which report room-temperature values fork1 of (6-S 2 3.4) X IO-l5 and < 2 X lo-t7 cm3 molecule-l s-l respectively_ More recently a third research group [5] has reported a room-temperature measurement by flash photolysis resonance absorption from which they calculate k, = (3-4 + 1.6) X IO-14 cm3 molecule-l s-l_ These results raise considerable doubt about the accuracy with which we know k, _ Coupled with recent observations [6-S] on the somewhat anomalous (negative) temperature dependence of the OH + HONO reaction 0H+HONO-,+H30+N03,
(2)
this latest study [5] may be used to suggest a non-negligible role for reaction (1) in removing stratospheric 0 009-2614/S3/0000-0000/o/s
03.00 0 1983 North-Holland
chlorine_ For example, if we accept the Clark et al [S] room-temperature value for lit and an E/R value of -1100 K [of comparable magnirude to the E/R of reaction (2)]. we find that reaction (1) can play a modest role in HCI formation in the midstratosphere relative to Cl + CH, and Cl + HO, [ 1.21. Cl+CH,+HCI+CH,,
(3)
Cl+HO,+HCI+O,_
(4)
The lack of any definitive information from the published studies on reaction (1) with which to either support or reject such speculation prompted us to conduct our own temperature dependence investigation of k, using the flash pliotolysis resonance fluorescence (FPRF) technique_ The results of these experiments at 243,264, and 298 K are reported in this communication_
2. Experimental Complete FPRF procedural details as well as information on the double-walled pyres reactor used in the present work may be found in our recent publication on the OH + HONO, reaction [7] _Chlorine atoms were produced via the flash photolysis of 12-30 mTorr of CCI, (1 mTorr = 0.133 Pa = 9_6SS7 X 1015/T(K) molecules cme3) at wavelengths longer than 165 nm. This range in Ccl, concentration coupled with changes in flash lamp pressure (intensity) permitted variation 281
CHEMICAL PHYSICS LETTERS
Volume 93, number 3
in initial Cl atom concentration, IO 3 x IO” cme3. The absence
[CIJO, from 3 X lOlo of any perceprible dependence of the atom decay rates on initial atom concentrarion was viewed as evidence for the lack of inrcrference from secondary arom-radical reactions in this range of [Cl],. The chlorine atom fluorescence resonantly scattered from rile microwave discharge resonanLy lamp (=O.l% Cl, in lie ai *I Torr) was viewed without wavelength resolution through a BaF, window (A 2 135 nm) using a solar blind photomultiplier and standard pulse caunkg eiecrronics. Fluoreswnce signal accumulated from multiple csperimcnts was stored in a microprocessor based multichannel analyzer system where the decay curves were analyzed assunting pseudo-firstorder kinetic behavior. &action mis~ures consisting of CCI, _HONO? _and either Ar or N, as a diluent gas were prepared manonxrrically in @ass storag bulbs prior to their being Ilowed through the reaction cell (~100 cm3 s-l) at prcssurcs berwecn 15 and 50 Torr. The nitric acid con-
ccntration
during each run was monitored
by optical
sbsorprion
(a = 1.63 X lo-l7 cm2 at iS4.9 nm) 16.9. IO] in a 10 cm ccl1 located on the exit port of the rcac-
IN. The light source for these measurements l’cn-r3?
was a Hg
is&red by a IS5 nm bandpass filter/ 0.25 111 Illo~locllron~ator combination. The reactant 11rw could hc divcrrcd directly inro the absorption hnp
cell.
bypassing the reactor. thereby providing a check on an) major HONO decomposition in the reaction cell. As in our earlier work. these procedures enabled us to monitor nitric acid concentrations with a precision of hc1Icr tlirtn 3 few percent.
21 January 1983
Table 1 Rare constants for the reaction Cl + HONO + HCI + NO3 T UQ
Dtiuent gas (Torr)
x-1 X 10” Standard (cm3 mole- deviation cule-’ s-l)
298
20 _4r, 20 Nz,SO N2
16-7
264
15 N2.20N2.50Nz
143
20N2,50N2
Total uncertainty
%l_O
+2.1 -5.2
8.4
21.0
+1.9 -3.3
4.6
51.4
+2.7 -3.5
cubic” for the first-order
Cl decay rate versus HONO, concentration data and took into account the uncertainties in both these variables [ 1 1] _The data at 29s K used for this analysis are shown in fig. l_ As can be seen we were forced to limit our studies to HONO? partial pressures below Z=100 mTorr due to the severe attenuation (absorption) [12,13] of the fluorescence signal between 135 and 140 nm by nitric acid. This, in turn. prevented us from conducting experiments over a very wide range of first-order decay rates thereby restricting the calculation of k, to runs exhibiting small differences in Cl atom lifetimes. Nevertheless a number of diagnostic tests were conducted to demonstrate that the amount by which our measured decay rates exceeded the diffusional loss rate of Cl was due primarily to the gas phase homogeneous title reaction.
?!itric acid was prepared by va~uu~~~ distilling a mixturn ~fdr?; sodium nitrate and concentrated sulfuric
:IA.
Following
purification
by trap-to-trap
distillation
in KIS srorcd 31 7S Ii until use. Spectrograde CC14 was dcgasscd via several freeze-pllIiip-thaw cycles prior 10 usr‘. Ultra high purity Ar and N, were used directly 1‘rom llic sylindcrs wiliioul further purification_
:i~
I 3. Results
’
and discussion
The results of our measurements at 743. 264? and 2% K arc summarized in table l_ The first column of unccrGlties rspressed for kl are the standard devia-
tiws from iIn itcrativc solution of tltc “least-squares
ris. I_ Plot of fast order decay rates, k. versus HONO concentration at 298 K. Diluent gas pressures: X, 20 Torr AI; o_ 20 Torr N1 ; +. 50 Torr Nz _
One of our first concerns was that signifkant production of OH from photolysis of the nitric acid could initiate secondary chemistry, not by direct reaction with Cl (which is expected to be slow) [14], but rather via rapid generation of NO, which could then react with Cl OH -I-HONO? + H,O -I-N03,
(2)
Cl+N03-+C10+N0,_
(5)
Indeed. modeling calculations showed that for initial concentrations of Cl and OH typical of our experiments. the apparent X-t value could increase signifkantly above 7 X 1O-‘5 for X-5 = I X 1 O--l1 cm3 molecule-*
s-I_ However, this result proved to be extremely sensitive to variations in [Cl]0 and [OH]0 in the IOtt cr1r3
region such that our experimental
variations in
flash
intensity should have yielded vastly differing first order decay raten We are therefore able to conclude generally that such secondary processes were insignificant in our experiments and more specific+ that k5 is substantially smaller than 1O-*l cm3 molecule-t s-t (the ritte constant [3] for the 0 + NO3 reaction). A second potential source of error in our measure-
ments was the contribution decays of the reaction
21 January 1983
CHEMICAL PHYSICS LElTERS
Volume 94, number 3
to the observed Cl atom
Cl + NO, + hl --f CINOz + hl,
(6)
where NO, could be present as an impurity in the nitric acid. There is no doubt that some of the fluctuations in our decay rate data are due to trace NO-, impurities or to NO, arising from HONO, decompisition. When extreme care was taken to thoroughly clean and bake out under vacuum all storage bulbs, the rcaclion cell. and its ancillary tubing such scatter was minimized and reasonably reproducible data could be obtained_ If one were to attribute the difference between our 30 Torr room-temperature data and the fit value of ref. [3] as being due to trace amounts of NO2 in our experiments, it would require a near constant NO, impurity level of 0.94%. This is in marked contrast to the 0.2-0.3% upper limit set from both analytical and kinetic considerations in our OH + HONO, study. Furthermore such an impurity level would have caused our measured decay rates to increase by nearly 80% in changing diluent gas pressure from 20 to.50 Torr_ As can be seen in fig. 1, our 20 Torr Ar, 20 Torr N2 1and
50 Torr N, data do not differ significantly in any statistically meaningful manner. A similar attempt at quantifying the difference between our work and that of ref. [4] leads to even more profound contradictions. The absence of a measurable pressure effect in our room-temperature data is itself consistent with the aforementioned OJ-03% upper limit on NO, since the latter would correspond to a change in slope in fig. 1 of 10 s-1 per lo0 mTorr HONO?. This in turn translates into a potential systematic overestimation of X-1at 29s K of 3.1 X 10-l” cm3 molecule-is-t. Thus if we take an extremely conservative approach and add this uncertainty to twice the statistical error we obtain Ii,(39SK)=(16_7+z:$X
IO-l5
cn~~n~olecule-ls-~.
Similar analysis can be performed for the 264 and 243 K data as well. These experiments were typified by much better reproducibility (less scatter) than the 298 K data suggesting that some slight decomposition of HONO occurring in the reaction cell at room temperature was minimized at the lower trmper~turcs. Thus we can place a more restrictive estimate on any systematic error in RI due to reaction (6) at these temFratures leading to the final column of uncertainties in table 1. It should be noted that despite the better reproducibility of the lower temperature data, the statistical uncertainties are greater than at 298 K due to the far greater number of experiments which were conducted at that temperature_ The three k, values are plotted in Arrhcnius form in fig.2 with the error bars of the final column of table 1 _
Fig_ 2. Arrhenius plot of X-i values from the presenr work. Solid line is I lean-squ;rrcs fir. Error bars xc csphincd in ihc test.
CHEhlICAL
PHYSICS
21 January
LETTERS
The compatibility
1983
of our data with an Arrhenius es-
pression characterized by a positive E/R of 1700 K strongly supports the original position [2] that the reaction of Cl atoms with nitric acid does not contribute appreciably to Cl atom removal in the midstratosphere. Similarly it has even less of an effect on the calculated nitric acid flux.
Acknowledgement
This work was supported bon
I’rogmrn
of the
Chenlical
in part by the FluorocafManufacturers
Associa-
and the Upper Atmospheric Research Program of the National Aeronautics and Space Administration tion
References .I 1 I- R.D. Iludson.
editor-incbicf, WhlO Global Ozone Rcstarch and hlonitoring Project. Report No. I I, The Str~tospbrrc 1961: Theory and hlcasurements. [ 21 \\‘.I& Dchlorc. R.T. Wason. D.hl. Golden. R-1:. Ilampson. h1.J. Kurylo. C.J. llowlrd. M.J. hlolina and A.R. Ravishankara. Clwmical Eimics and Iahotochcniic~l Lktn for Use in Stratospbcric hlodcling. J.P.L. Publintion 82-57 (15 July 1961). 131 hl.-T. Lcu aud W.B. Dc>lorc. Cbcm. Pbys. Lcttcrs 41 (1976) 1’1. J. Cbem. Pbys. I41 G. I’oulc~. C. LeIIrasand J. Combouricu, 69 (1978) 767. I-‘1 K.11. Clark, D. llumin and J.Y. Jezcqucl. J. Photocbem. 18 (1982) 39. N.hl. Krcultcr, R.C. Shah. 161 P.11. Wine, A.R. Rwislnnkarii, JAI. Nicovich, Geophys.
R.L. Thompson
and D.J. Wuebblcs,
J.
Rcs. 86 (198 1) I 105.
I71 hl.J. Kurylo.
llcs. 67 (1982)
IS1 J -1. hlargitan
K-1). Cornctt and J.L. Murphy. J. Ceophys. 3081. and R.T. Watson. J. Phys. Cbcm.. lo bc
published. 191 l-‘. Binume. J. I’hotochem. I! (1973) 139. 1101 11-N. N&on. WJ. hlxinelli and H.S. Johnston, Chem. Phys. Letters 78 (1961) 495. 1111 D. York. fin. J. Phys.44 (1966) 1079. and K_P. Wayne, J. Photo1131 GS. Ueddard. D-J. Cixbxdi them. 3 (1974175) 321. 1131 II. Okabc. J. Chcm. Phys. 72 (1980) 6642. and the StratoI141 R.D. Hudson, cd., Cblorofluoromethancs sphere. NASA RP IO IO (August 1977).