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MOTIVATIONS : Atmospheric Chemistry

MOTIVATIONS : Atmospheric Chemistry. Troposphere Chemistry – Ozone Production RO 2 + NO → RO + NO 2 NO 2 → NO + O( 3 P) O( 3 P) + O 2 + M → O 3 + M. MOTIVATIONS : Low Temperature Combustion.

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MOTIVATIONS : Atmospheric Chemistry

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  1. MOTIVATIONS : Atmospheric Chemistry Troposphere Chemistry – Ozone Production RO2 + NO → RO + NO2 NO2 → NO + O(3P) O(3P) + O2 + M → O3 + M

  2. MOTIVATIONS : Low Temperature Combustion M. J. Pilling, Comprehensive Chemical Kinetics, 35, 1(1997)

  3. L Intensity t0 R tabsorber Time ( L / c ) t = ( L / c ) (a) 0 - 1 R t = (b) - s 1 R n l + Cavity Ringdown Absorption Spectroscopy A = nsl A = L/ctabsorber - L/ct0 Sensitive L=1m Leff=10 km t0=34 ms R=0.99%

  4. Experimental Setup DCM & Rhodamine B/101 650 – 700 mJ 90 – 130 mJ YAG 532 nm Sirah Dye Laser 580 – 640 nm Filters 1.5 - 1.1 mm H2 Raman Cell 2nd Stokes High Reflectivity Mirrors 1 – 2 mJ Ringdown Cell PD ArF 193 nm 160 – 200 mJ

  5. Origin of the A2A- X2A Electronic Transition of CH3O2 • Reaction* • Initiation: • Precursor + hν R+(CO, Br , I, CO2) • Production: • O2+R+M  RO2+M • Radical-Radical Losses: • R+R+M  R2+M • R+RO2  2RO • RO2+RO2 Products *precursor for CH3 - acetone / methyl iodide

  6. ~ Origin of the A2A- X2A Electronic Transition of CH3O2 / 0-0 cm-1 M. B. Pushkarsky, S. J. Zalyubovsky, and T. A. Miller, J. Chem. Phys.112, 10695 (2000)

  7. MOTIVATIONS : Why C6H5O2 and How ? The reaction of phenyl radical (C6H5) with molecular oxygen is postulated to impede the formation of soot inherent in hydrocarbon combustion, according to the following mechanism. O2 C6H5O2

  8. Production of C6H5 radical from Acetophenone at 193 nm 3 Channels C6H5CO + CH3 (1) C6H5COCH3 + hv  C6H5 + CH3CO (2) C6H5COCH3 + hv  C6H5CH3 + CO (3) C6H5COCH3 + hv  (1) and (2) have comparable cross sections. Cross section for channel (3) is estimate to be less than 0.1 % of those processes (1) and (2). 30 – 50 % of primary C6H5CO further decomposes, yielding secondary products C6H5 + CO and CH3 + CO respectively Zhao, H.-Q. et al. Journal of Chemical Physics (1997), 107(18), 7230-7241.

  9. Photolysis of acetophenone at 193 nm Bond Origin Acetophenone at 193 nm (1)Acetone at 193 nm (1) M. B. Pushkarsky, S. J. Zalyubovsky, and T. A. Miller, J. Chem. Phys.112, 10695 (2000)

  10. Comparaison with other precursors PhO2 MeO2 Bromobenzene at 193 nm Acetophenone at 193 nm (1)Acetone at 193 nm

  11. Photolysis of acetophenone at 193 nm Band Origin PhO2 MeO2 PhO2

  12. Photolysis of acetophenone at 193 nm O-O Stretch PhO2 MeO2 MeO2

  13. Tentative assignment O-O stretch 1401 1201

  14. Tentative assignment 2301

  15. Tentative assignment Zoom 000 3311 3322 3333

  16. Assignment 3301

  17. Conclusion andFuture Work ~ ~ • We have observed theA2A' –X2A" electronic transition of phenyl peroxy radical. • Assignment has been done. • Studying other unsaturated peroxy radicals and other peroxy radicals (C5H11O2). ~ ~

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