Little Things Mean a Lot Total Pressure: 20-200Torr H20 1-10 ppm 03 1-10 ppm CIo 0.1-3ppb BrO 1 ppt 0 1 ppt-1ppb C 0.1 ppt-10 ppt VI-11
Total Pressure: 20-200 Torr H2O 1-10 ppm O3 1-10 ppm ClO 0.1-3 ppb BrO 1 ppt O 1 ppt-1ppb Cl 0.1 ppt-10 ppt Little Things Mean a Lot VII-11
Free radicals a:0 Molecule with odd number of electrons “Open Shell'' Typically highly reactive Some atmospheric radicals Cl,Br H 0 CIO OH NO BrO 02H VI-12
Molecule with odd number of electrons “Open Shell” Typically highly reactive Some atmospheric radicals Cl, Br H O ClO OH NO BrO O2H Free Radicals :Cl:O. •• •• •• •• VII-12
Radical Chain reactions Initiation Cl2+hvCl·+Cl. Propagation (by each Cl atom) CI+CH4→HCI+.CH CH3+C2→CHCI+CI· Etc.,etc.....until Termination (example) C1.+.C1→Cl2 or C1·+CH3→CH3CI One photon can lead to 10n reactions VI-13
Initiation Propagation (by each Cl atom) Termination (example) One photon can lead to 10n reactions Cl2 + hν Cl + Cl Cl + CH4 HCl + CH3 CH3 + Cl2 CH3Cl + Cl Etc., etc…..until Cl + Cl Cl2 or Cl + CH3 CH3Cl . Radical Chain Reactions . . . . . . . . . VII-13