the the Gas Phase (CH Gas Phase (CH 3 3 ) ) 2 2 S S – – Br Adduct Br Adduct V. Dookwah-Roberts V. Dookwah-Roberts 1 , R.J.H. Lee , R.J.H. Lee 2 , , J.M. Nicovich J.M. Nicovich 2 , and P.H. Wine , and P.H. Wine 1,2 1,2 1 School of Earth & Atmospheric Sciences School of Earth & Atmospheric Sciences 2 School of Chemistry & Biochemistry School of Chemistry & Biochemistry Georgia Institute of Technology Georgia Institute of Technology 4th EAS Graduate Student Symposium, Atlanta GA, November 10 4th EAS Graduate Student Symposium, Atlanta GA, November 10 th th 2006 2006
18
Embed
Kinetics and Spectroscopy of the Gas Phase (CH 3 ) 2 S – Br Adduct
Kinetics and Spectroscopy of the Gas Phase (CH 3 ) 2 S – Br Adduct. V. Dookwah-Roberts 1 , R.J.H. Lee 2 , J.M. Nicovich 2 , and P.H. Wine 1,2 1 School of Earth & Atmospheric Sciences 2 School of Chemistry & Biochemistry Georgia Institute of Technology - PowerPoint PPT Presentation
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
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.
●● 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.
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
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.