大气光化学new

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1、Photochemistryintheatmosphere1.Radiationintheatmosphere2.Elementaryphotochemicalprocesses3.Photodissociationofoxygenandozone1.Photodissociationofoxygen2.Photodissociationofozone4.Photochemicallayers5.OiOverviewofatmosphhiericphhliotolyticreactionsVíctorJHerreroVíctorJ.Herrerovherrero@iem.c

2、fmac.csic.esRadiationintheatmosphereóMostoftheenergyfluxreachingtheEarthiselectromagneticradiationemittedbytheSunóTheaveragevalueoftheradiantfluxdensityreachingasurfaceelementperpendiculartotheSun‐Earthdirectioniscalledsolarconstant(1370W/m2)óThesolaremissionspectrumresemblesthatofablackbo

3、dyatT ≈ 5800K,i.e.withamaximuminthevisible.óAverysmallamount(<10‐9W/m2)ofhihlhighlyenergeticparticles(mostlyprotons)reachestheEarthassolarwindorcosmicradiationSolar)mLyman-α/nStSpectrum2ity(mW/mOuteratmospherentFluxDensaSunBlackbodyat5800KRadiWavelength(nm)Earth’ssurfaceBondbreakingandioni

4、zationBondenergyIonizationenergyeVnmeVnmNO23.113999.78127N2O(N‐N)4.4328012.8996N2O(N‐O)1671.67743O31.04119212.5299H2O5.1224212.6198CO25.4522813.7990N29.7612712.5880O25.1124312.07103NO6.501919.26134CO11.0911214.0189AbsorptionofUVradiationóTheshortestwavelengthradiationisabsorbedintheupperat

5、mosphereMoleculeλforstrongabsorptionO3<290nmO2<200nmHOH2O<180nmCO2<165nmN2<100nmH2<100nmnmActinicfluxóF(λ)istheamountoflightavailabletoamoleculeatagivenpointintheatmosphereóItincludes,direct,reflected,andscatteredradiationOO23Zenithangle,33ºAlbedo,0.3Elementary(primary)photochemicalprocess

6、es•Quantumyield:EmissionofradiationóGeneralóΔE=hvóSelectionrules(symmetry,angularmomenta)óFranck‐Condonfactors(nuclearconfiguration)óIntensity~ ν3óFluorescenceóConservationofspin(S‐S,T‐T)óLifetime(10‐7‐10‐9s)óPhosphorescenceóSpinforbidden(T‐S)óLifetime(10‐3‐102s)Non-radiativetransitionsóTh

7、estateinitiallyexcitedcantransferitsenergytootherstatesofsimilarenergyóInternalconversionóTransfertoastateofthesamemultippylicityóIntersystemcrossingóTransfertoastateofdifferentmultiplicityPhotodissociationóMolecularfragmentationuponabsorptionofradiationóOptic