Kinetics and Spectroscopy of the Kinetics and Spectroscopy of the
Gas Phase (CHGas Phase (CH33))22SS––Br AdductBr Adduct
V. Dookwah-RobertsV. Dookwah-Roberts11, R.J.H. Lee, R.J.H. Lee22,,
J.M. NicovichJ.M. Nicovich22, and P.H. Wine, and P.H. Wine1,21,2
11 School of Earth & Atmospheric Sciences School of Earth & Atmospheric Sciences
22 School of Chemistry & Biochemistry School of Chemistry & Biochemistry
Georgia Institute of TechnologyGeorgia Institute of Technology
4th EAS Graduate Student Symposium, Atlanta GA, November 104th EAS Graduate Student Symposium, Atlanta GA, November 10 thth 2006 2006
MOTIVATIONMOTIVATION
●● DMS (CHDMS (CH33SCHSCH33) accounts for 10-30 % of ) accounts for 10-30 % of
the total sulfur flux to the atmosphere.the total sulfur flux to the atmosphere.
●● DMS oxidation impacts cloud formation overDMS oxidation impacts cloud formation over
oceans => climate effects.oceans => climate effects.
●● BrOBrOxx radicals represent one important DMS radicals represent one important DMS
oxidant in the marine environment.oxidant in the marine environment.
Literature Summary: Br + DMS ↔ Br-DMSLiterature Summary: Br + DMS ↔ Br-DMS
●● Wine et al., in Wine et al., in NATO ASI Ser., Vol I7, NATO ASI Ser., Vol I7, Ed. by H. Ed. by H.
Niki & K.H. Becker, 1993, 385.Niki & K.H. Becker, 1993, 385.
●● Ingham et al., J. Phys. Chem. A 1999, 103, 7199 Ingham et al., J. Phys. Chem. A 1999, 103, 7199
● ● Nakano et al., J. Phys. Chem. A 2001, 105, 11045 Nakano et al., J. Phys. Chem. A 2001, 105, 11045
Goals of this StudyGoals of this Study
●● 11stst study of adduct kinetics study of adduct kinetics
●● Map spectrum in region 300 – 500nm. Compare results Map spectrum in region 300 – 500nm. Compare results with Ingham et al. and Nakano et al.with Ingham et al. and Nakano et al.
●● Assess reactivity trends in reactions of weakly-bound Assess reactivity trends in reactions of weakly-bound halogen atom adducts with atmospheric gases.halogen atom adducts with atmospheric gases.
Experimental ApproachExperimental Approach
●● Laser flash photolysis − time−resolved Laser flash photolysis − time−resolved
UV−vis absorption spectroscopyUV−vis absorption spectroscopy
●●T = 265 K; P = 200 Torr NT = 265 K; P = 200 Torr N22/O/O22
●● Source of Br in all experiments:Source of Br in all experiments:
CFCF22BrBr22 + h + hνν(248(248 nm) →nm) → Br + CFBr + CF22BrBr
Time−resolved absorption dataTime−resolved absorption data
265 K, 200 Torr265 K, 200 Torr NN22, , λλ = 365 nm = 365 nm
The observed absorption is coming from a product of Br + CH3-S-CH3 (almost certainly the CH3S(Br)CH3 adduct).
16
14
12
10
8
6
4
Ab
sorb
ance
x 1
000
400300200100
Time (s)
70
60
50
40
30
20
10
0
k a (
103 s
-1)
76543210
[DMS] (1014
molecules cm-3
)
9.12 x 10-11
Absorption SpectrumAbsorption Spectrum
at 338 nm is much smaller than found by Nakano et al.
but spectrum agrees well with Ingham et al.
30
25
20
15
10
5
0
(1
0-18
cm2
mo
lecu
le-1
)
550500450400350
Wavelength (nm)
Our data
Ingham et al.
Radical − Radical Reaction KineticsRadical − Radical Reaction Kinetics
T = 265 K, P = 200 Torr NT = 265 K, P = 200 Torr N22
[Br-DMS[Br-DMS] / [Br] ~ ] / [Br] ~ 178178
Slope (red line) givesSlope (red line) gives
2k = (3.29 2k = (3.29 ±± 0.04) x 10 0.04) x 10−−1010 cm cm33molecmolec−−11ss−−11
((Br-DMSBr-DMS + + Br-DMSBr-DMS → products) → products)
Average of 26 expts. like the one
shown on the right gives
2k = (3.0 ± 0.3) x 10−10 cm3molec−1 s−1
(uncertainty is 2σ, precision only).
1.0
0.8
0.6
0.4
0.2
0.0
[Br-
DM
S]-1
(10
-12cm
3m
ole
cule
-1)
1.00.80.60.40.20.0
Time (ms)
Adduct + OAdduct + O22 Reaction Kinetics Reaction Kinetics
T = 265 K; P = 200 Torr OT = 265 K; P = 200 Torr O22; [DMS] = 1.6 x 10; [DMS] = 1.6 x 101515 per cm per cm33; [Br]; [Br]00 ≈ 1 x 10 ≈ 1 x 101313 per cm per cm33..
Simulations suggest that upward curvature in the [Br-DMS]Simulations suggest that upward curvature in the [Br-DMS]−1−1 vs. time plot would be vs. time plot would be
observable if the Br-DMS + Oobservable if the Br-DMS + O22 rate coefficient was > 1 x 10 rate coefficient was > 1 x 10−17−17 cm cm33molecmolec−1−1ss−1−1..
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0[Br-
DM
S]-1
(10
-12 c
m3 m
ole
cule
-1)
2.01.51.00.50.0Time (ms)
01E-17
5E-17
3E-17
Br-DMS + O2
Adduct + NO/NOAdduct + NO/NO22 Reaction KineticsReaction KineticsExperimental conditions of low T (265 K), P (200 Torr N2), low [Br]0, and high [DMS] are employed to minimize interferences from radical − radical reactions and Br + NOx reactions.
-9
-8
-7
-6
-5
-4
ln A
bs
orb
an
ce
250200150100500Time (s)
Br-DMS + NO
4
3
2
1
0
k d (
104 s
-1)
2520151050
[NOx] (1014
molecules cm-3
)
NO2
NO
2.6 x 10-11 1.3 x 10
-11
speciesspecies
kkO2O2
(10(10-18-18 cm cm33 molecule molecule-1-1 s s-1-1))
kkNONO
(10(10-11-11 cm cm33 molecule molecule-1-1 s s-1-1))
kkNO2NO2
(10(10-11-11 cm cm33 molecule molecule-1-1 s s-1-1)) referencesreferences
Br-DMSBr-DMS
Cl-DMSOCl-DMSO
CHCH33I-ClI-Cl
CC22HH55I-ClI-Cl
CSCS22-Cl-Cl
Cl-DMSCl-DMS
< 2 < 2
< 3< 3
< 30< 30
< 10< 10
< 5< 5
< 4< 4
(1.3 (1.3 ± 0.2)± 0.2)
(1.2 (1.2 ± 0.3)± 0.3)
(2.0 (2.0 ± 0.2)± 0.2)
(2.0 (2.0 ± 0.2)± 0.2)
(2.2 (2.2 ± 0.5)± 0.5)
(1.2 (1.2 ± 0.2)± 0.2)
(2.6 (2.6 ± 0.2)± 0.2)
(2.1 (2.1 ± 0.3)± 0.3)
(3.5 (3.5 ± 0.4)± 0.4)
(3.9 (3.9 ± 0.5)± 0.5)
(1.3 (1.3 ± 0.4)± 0.4)
(2.7 (2.7 ± 0.4)± 0.4)
this workthis work
aa
this workthis work
this workthis work
bb
cc
Summary of Reaction Kinetics of Summary of Reaction Kinetics of Halogen Adducts with OHalogen Adducts with O22, NO and NO, NO and NO22
a. Kleissas, K.M.; Nicovich, J.M.; Wine, P.H. J. Photochem. In press. b. Dookwah-Roberts, V.; Soller, R.; Nicovich, J.M.; Wine, P.H. J. Photochem. 2005, 176, 114-123. c. Urbanski, S.P.; Wine, P.H. J. Phys. Chem. A 1999, 103, 10935-10944.
SUMMARYSUMMARY
●● maxmax and and maxmax obtained agree well with obtained agree well with
Ingham et al. but Ingham et al. but at 338 nm is a factor of at 338 nm is a factor of 7 smaller than obtained by Nakano et al. 7 smaller than obtained by Nakano et al.
●● Kinetic data obtained for 1Kinetic data obtained for 1stst time. time.
●● Rate constants similar to other adducts Rate constants similar to other adducts studied eg. SCS-Cl, DMS-Cl, DMSO-Cl. studied eg. SCS-Cl, DMS-Cl, DMSO-Cl.
Future DirectionsFuture Directions
●● Conduct pressure dependent study of Conduct pressure dependent study of
BrO + DMS reaction kinetics.BrO + DMS reaction kinetics.
AcknowledgmentsAcknowledgments
Research Group Members (non-authors)Research Group Members (non-authors)
Zhijun Zhao Dow HuskeyZhijun Zhao Dow Huskey Andrew Mudd Andrew Mudd
Patrice BellPatrice Bell Katie Olsen Katie Olsen
Support $$$Support $$$
NSF & NASANSF & NASA
Comparative SpectroscopyComparative Spectroscopy
________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
AdductAdduct λλmax max (nm)(nm) FWHM (nm) FWHM (nm) σσmax max (10(10−18−18 cm cm22) ) aa
__________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
SCS−Cl SCS−Cl bb 365 365 23 23 23 23 480480 85 85 3.9 3.9
(CH(CH33))22S−Cl S−Cl c,dc,d 340 340 75 75 35 35
(CH(CH33))22(O)S−Cl (O)S−Cl ee 390 390 100 100 21 21
(CH(CH33))22S−Br S−Br ff 365 365 75 75 27 27
________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
a a Uncertainties are typically 30−40%.Uncertainties are typically 30−40%.b b Dookwah-Roberts, Soller, Nicovich, and Wine, Dookwah-Roberts, Soller, Nicovich, and Wine, J. Photochem. Photobiol. A: ChemJ. Photochem. Photobiol. A: Chem., submitted (this work).., submitted (this work).c c Urbanski & Wine, Urbanski & Wine, J. Phys. Chem. A J. Phys. Chem. A 19991999, , 103103, 10935., 10935.dd Enami, Nakano, Hashimoto, Kawasaki, Aloisio, & Francisco, Enami, Nakano, Hashimoto, Kawasaki, Aloisio, & Francisco, J. Phys. Chem. AJ. Phys. Chem. A, , 20042004, , 108108, 7785., 7785.e e Wine, Nicovich, McKee, Kleissas, Parthasarathy, Pope, &Pegus, 18Wine, Nicovich, McKee, Kleissas, Parthasarathy, Pope, &Pegus, 18 thth Intl. Symp. on Gas Kinetics, Bristol, UK, 2004, to Intl. Symp. on Gas Kinetics, Bristol, UK, 2004, to
be published.be published.ff Ingham, Bauer, Sander, Crutzen, & Crowley, Ingham, Bauer, Sander, Crutzen, & Crowley, J. Phys. Chem. AJ. Phys. Chem. A 1999 1999, , 103103, 7199., 7199.
FM
FM
PMTPG MIX
ING
CE
LL
REACTION CELL
EXCIMER LASER
Cl2CO/N2
N2 or O2
CS2
NO/NO2/ N2
Cl2CO MONITOR
FM
FM
OSCILLOSCOPE
COMPUTER
PMT
ARC LAMP
MONOCHROMATOR
HV
PM
T
BPF
TO PUMP
CS2 MONITOR
Zn LAMPPMT
BPF
COOLANT out
COOLANT in
Zn LAMP
TP TP
HR 248
HR 248
LFP−TRUVVASApparatus
Comparative KineticsComparative Kinetics
__________________________________________________________________________________________________________________________________________________________________________________________________________________________________
AdductAdduct kkO2O2aa
kkNONOaa k kNO2NO2
aa
__________________________________________________________________________________________________________________________________________________________________________________________________________________________________
SCS−Cl SCS−Cl bb < 5 x 10 < 5 x 10-5-5 220 220 130 130
(CH(CH33))22S−Cl S−Cl cc < 4 x 10 < 4 x 10−5−5 120 120 270 270
(CH(CH33))22(O)S−Cl (O)S−Cl dd < 1 x 10 < 1 x 10−5−5 150150 190 190
SCS−OH SCS−OH 0.29 0.29 e,f,ge,f,g 7.3 7.3 gg 420 420 g g
(CH(CH33))22S−OHS−OH 9.6 9.6 h,i h,i
__________________________________________________________________________________________________________________________________________________________________________________________________________________________________
a a Units are 10Units are 10−13 −13 cmcm3 3 molecmolec−1 −1 ss−1−1..
b b Dookwah-Roberts, Soller, Nicovich & Wine, Dookwah-Roberts, Soller, Nicovich & Wine, J. Photochem. PhotobiolJ. Photochem. Photobiol. . A: Chem, A: Chem, submitted (this work). submitted (this work). c c Urbanski & Wine, Urbanski & Wine, J. Phys. Chem. A J. Phys. Chem. A 19991999, , 103103, 10935. , 10935. d d Wine, Nicovich, McKee, Kleissas, Parthasarathy, Pope, & Pegus, 18Wine, Nicovich, McKee, Kleissas, Parthasarathy, Pope, & Pegus, 18thth Intl. Symp. on Gas Kinetics, Bristol, UK, 2004, to be published. Intl. Symp. on Gas Kinetics, Bristol, UK, 2004, to be published.e e Hynes, Wine, & Nicovich, Hynes, Wine, & Nicovich, J. Phys. Chem. J. Phys. Chem. 19881988, , 9292, 3846. , 3846. f f Murrells, Lovejoy, & Ravishankara, Murrells, Lovejoy, & Ravishankara, J. Phys. Chem. J. Phys. Chem. 1999, 1999, 2381.2381.g g Diau & Lee, Diau & Lee, J. Phys. Chem. J. Phys. Chem. 19911991, , 9595, 7726., 7726.h h Hynes, Stoker, Pounds, McKay, Bradshaw, Nicovich, & Wine, Hynes, Stoker, Pounds, McKay, Bradshaw, Nicovich, & Wine, J. Phys. Chem.J. Phys. Chem. 19951995, , 9999, 16967., 16967.i i Barone, Turnipseed, and Ravishankara, Barone, Turnipseed, and Ravishankara, J. Phys. Chem. J. Phys. Chem. 19961996, , 100100, 14694., 14694.
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