Direct Observation of the C S 2 Channel in CS 2 Photodissociation - Li et al. - 2021 - Unknown

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pubs.acs.org/JPCLLetterDirectObservationoftheC+S2ChannelinCS2PhotodissociationZhenxingLi,MinZhao,TingXie,ZijieLuo,YaoChang,GongkuiCheng,JiayueYang,ZhichaoChen,WeiqingZhang,GuorongWu,XinganWang,*KaijunYuan,*andXuemingYangCiteThis:J.Phys.Chem.Lett.2021,12,844−849ReadOnlineACCESSMetrics&MoreArticleRecommendations*sıSupportingInformationABSTRACT:Carbondisulfide(CS2)isatypicaltriatomicmolecule.Itsphoto-dissociationprocesshasgenerallybeenassumedtoproceedtoCSandSprimaryproductsviasinglebondfission.However,recenttheoreticalcalculationssuggestedthatanexitchanneltoproduceC+S2shouldalsobeenergeticallyaccessible.Here,wereportthedirectexperimentalevidencefortheC+S2channelinCS2photodissociationbyusingthevelocitymapionimagingtechniquewithtwo-photonUVandone-photonvacuumUV(VUV)excitations.ThedetectionoftheC(3P)productsillustratesthatthegroundstateandtheelectronicallyexcitedstatesofS2coproductsareformedwithinhighlyexcitedvibrationalstates.Theveryweakanisotropicdistributionsindicaterelativelyslowdissociationprocesses.ThepossibledissociationmechanisminvolvesmolecularisomerizationofCStolinear-CSSfromtheexcited1B(21Σ+)stateviavibronic22couplingwiththe1Πstatefollowedbyanavoidedcrossingwiththegroundstatesurface.OurresultsimplythattheS2moleculesobservedincometsmightbeprimarilyformedinCS2photodissociation.17−19hotodissociationdynamicsoftriatomicmoleculeshasvariesremarkably,from0.25to6.ForphotolysisPbeenafieldofintensiveresearch,asthesesystemsarewavelengthstowardthevacuumultraviolet(VUV)region,theproductionoftripletCS(a3Π)becomesmoreimportant,amenabletodetailedexperimentalandtheoreticalstudiesthatcouldsignificantlydeepenourunderstandingofphoto-andbetween140and125nm,theCSfragmentsarealmost20chemistry.Overthepastfewdecades,thetextbookmechanismcompletelyproducedinthetripletstate.ThepossibleforatriatomicmoleculeABCmainlyinvolvessinglebonddissociationchannelsconcerningCSandSfragmentsarefissiontoproduceA+BCorAB+C.1However,recentsummarizedinFigure1.investigationsonCO(linear−OCO)2andOCS3photolysisRecently,theCSandS2radicalshavebeenbothobservedby221haverevealedthecentral-atomeliminationprocesses,i.e.,C+radioandultraviolet(UV)spectroscopiesinseveralcomets.O2andC+SOchannels,whichcouldtakeplaceviaeitheraTheoreticalcalculationssuggestedthattheUVirradiationofDownloadedviaUNIVOFCONNECTICUTonMay16,2021at07:41:14(UTC).conventionalnonadiabaticdissociationpathwayoraroamingCS2mayinducephotochemicalprocessesresponsibleforthe22pathway.Intriguingquestionswouldbedoesthiscentral-atomproductionofCSandS2radicalsincomets.Ontheothereliminationchannelexistinthephotodissociationprocessesofhand,Jimenz-Escobarandco-workersproposedH2S2,formedSeehttps://pubs.acs.org/sharingguidelinesforoptionsonhowtolegitimatelysharepublishedarticles.othertriatomicmoleculesanddoesthisprocessinvolveaftertheX-rayradiationofH2Sices,astheparentforS223anotherdetailedmicroscopicmechanism?productionincomets.Infact,whetherS2is“aparentoraAsatypicaltriatomicmolecule,CSpossesses16valencedaughter”isstillunknown;regardless,S2isveryshort-lived.2Althoughonespeculatesthatthecentral-atomeliminationelectronswithalinearcentrosymmetricstructure(SCS).channelmaywidelyexistinthephotodissociationprocessesofBecauseofitsimportanceinastrophysicalmedia,theearth’striatomicmolecules,suchaprocesshasnotbeenobservedinatmosphere,biologicalmedia,andorganicchemistry,thephotodissociationbehaviorofitslow-lyingsingletandtriplettriatomicmoleculesystemsotherthanCO2andOCSyet.4−8TherehavebeenseveralreportsofCS2photochemistrythatelectronicstateshavebeenextensivelystudiedtheoretically9−13havetriedtoillustratetheformationmechanismofS2andexperimentally.TheabsorptionspectrumofCS22414fragments.Inonestudy,deSorgoetal.observedtransientshowsmanyabsorptionbandsbetween100and400nm,andthephotochemistryofCS2inthisregionhasbeenasubjectofactiveinterestformorethanhalfacentury,duetoitsReceived:November13,2020strongdependenceonthewavelengthofphotolysis.Accepted:January7,2021Absorptionofonephotonaround193nmleadstothePublished:January11,2021productionofsingletCS(X1Σ+)fragmentsandsulfuratomsinthetripletorsingletstate(3Por1D).15,16ThebranchingratiofortheS(3P)andS(1D)channelsreportedfromthesestudies©2021AmericanChemicalSocietyhttps://dx.doi.org/10.1021/acs.jpclett.0c03386844J.Phys.Chem.Lett.2021,12,844−849

1TheJournalofPhysicalChemistryLetterspubs.acs.org/JPCLLetterpropagatingalongthecenteraxisoftheionopticsassemblymountedinthesamedifferentiallypumpedreactionchamber.Themolecularbeamwasintersectedat90°anglesbythephotolysisandprobelaserbeamsbetweenthesecondandthethirdplatesoftheionopticsassembly.ThephotolysisphotonswereprovidedbyanNd:YAGlaserpumpeddyelaser(fortwo-photonexcitationbetween300and320nm)andthevacuum33,34ultravioletfreeelectronlaser(theVUVFEL,forone-photonexcitationbetween128and144nm).TheC(3P)photoproductswereprobedby1+1′(VUV+visible)excitationwiththeλVUV=127.99nm(resonantexcitationofC(3P)).35TheVUVdetectionlaserlightwasgeneratedbythe1four-wavedifferencefrequencymixingthefrequencydoubledoutputfromonedyelaser(atλ=212.557nm)andthefundamentaloutputofaseconddyelaser(atλ=626.57nm)inaKrgascell.Thevisiblelaserbeam(atλ=700nm)generatedbyathirddyelaserwasusedasthe1′light.TheC+Figure1.PlausiblemechanismsofthephotodissociationofCS2.(i)ionswerethenacceleratedthroughtheremainingionopticsTwo-photonexcitationwiththewavelengthsbetween300and320anda740mmlongfield-freeregionbeforeimpactinga70mmnm.(ii)One-photonexcitationbyusingtheVUVFELlaserinthediametermicrochannelplate(MCP)detectorcoupledwithawavelengthregionof128−144nm.(iii)Thewavepacketexploresthe11+phosphorscreen(P43).Acharge-coupleddevice(CCD)flatpotentialenergysurfaceofB2(2Σ),andspin−orbitorvibroniccamerawasusedtorecordthetransientimagesonthecouplingsmayoccur,leadingtoS+CSorconversiontolinearCSS.phosphorscreen,usinga15nsgatepulsevoltageinordertoacquiretime-slicedimages.absorptionspectraofS2(v=0),butnoSatomswereobservedAsmentionedabove,wefirstemployedtwo-photonbythatmethod.TheyconcludedthatS2mustbeformedbyexcitationofCS2inthewavelengthregionof300−320nmthereactionCS2*+CS2→2CS+S2.Inotherstudies,andVUV+visiblelightbeamstoionizetheCatomproducts.2526Figure2presentstheionimagesofC(3P)productsattwo-MakarovandBazhin,andmorerecentlyMakarov,1suggestedtheformationofSwouldprobablyoccurinsmallphotonphotolysiswavelengthsof300.0,303.8,307.3,312.9,2clustersofCSandprovidedamodelforanewstyleofclusterand320.0nm.Thedoubleheadedredarrowsinthefigures2photochemistry:(CS2)2*→(CS)2+S2.Morerecently,Sapersstandforthepolarizationdirectionofphotolysislasers.Theetal.27proposedthatCSexcitedintheregionof300nmwell-resolvedconcentricringstructureswereobservedinthe2absorbsasecondphotonwithahighcrosssectiontoahigh-ionimages,whichcorrespondtoindividualvibrationalstatesoflyingstateataround8.05eV,wherethemoleculeS2coproducts.ItisnotedthatthesestructurescannotarisepredissociatestoCS+S;theSatomsthusthenreactwithfromtheotherCeliminationprocess,liketheC+S+SCS2togiveS2andCS.Todate,however,thedirectevidenceofchannel,becauseoftheinsufficientphotolysisphotonenergy.theS2productfromCS2photolysishasnotyetbeenobserved.ToavoidtheCfragmentfromthesecondarydissociation(theRecenttheoreticalcalculation28byTrabelsietal.suggestedprimaryCSfragmentmayfurtherdissociatebyabsorbingonethatanexitchanneltoproduceC+S2fromCS2photolysisUVorVUVphoton),anoff-axisbiconvexLiFlenswasusedtowithsufficientphotonenergyispossible.Thecomputationdispersethe212.557nmlightfromthedirectionof127.99nm35showedthatforbentstructures,theinitiallyexcited1B(21Σ+)beam,andthe127.99nmlightremainsdefocused.2stateofCSiscrossedbythebentcomponentofthe1Πstate;InthisCS2photodissociationexperiment,thephoto-23theCSSisomercanbeformedaftervibroniccouplingwith1Πexcitationenergy(hv)isdistributedbetweentheC(PJ)andS(X3Σ−)productkineticenergy(E)andinternalenergybyanavoidedcrossingwiththegroundelectronicstate.As2gK(E),whereE[C(3P)]isduetoexcitationofthespin−orbitshowninFigure5binref28,theformationofthecyc-CS2intintJstate;andthecorrelatedS(X3Σ−)photoproductscanbefromthelinearCSStakesplaceontheflatpotentialenergy2gsurfaceofthegroundstateofthelinearCSS.TheCSSbothrotationallyandvibrationallyexcited.TheVMIimagesmoleculehasenoughinternalenergytoconverttocyc-CS2orcanbeusedtodeterminetherecoilvelocitydistributionofthe3viafragmentation,producingC(3P)+S(X3Σ−).DespiteC(PJ)photofragmentsfromtheradiioftheresolvedring2gthesetheoreticalresults,toourknowledge,therehasbeennostructures.Thevelocitiesareconvertedtoatotalkineticenergyrelease(TKER)spectrumoftheC(3P)+S(X3Σ−)channelexperimentalverificationoftheC+S2channelinCS2J2gphotodissociation.Here,wereportthestudyofthisinterestingbyusingeq1basedontheconservationoflinearmomentumC+S2channelinCS2photodissociationbyusingtwo-photonandenergyandone-photonexcitations.DirectexperimentalevidenceofC33−−3333−11+hv=+[D0iEntC(P)JJ]+[Σ]EintS(X2gK)+[EC(P)+S(X2Σ]g)(P)+S2(XΣg/aΔg/bΣg)productswasobservedusing3(1)thevelocitymapionimaging(VMI)measurementsofC(P)atoms.ThephotoconversionofCS2tocyc-CS2andlinear-CSSHere,D0isthethermochemicalthresholdfortheformationofisbelievedtoplayanimportantroleinthisdissociationtheC(3P)+S(X3Σ−)productsfromCSdissociation,J2g2process.whichwasdeterminedtobe7.86eV(157.7nm)byFournier36TheapparatusfortheVMIexperimentshasbeendescribedetal.However,ourexperimentshaverecordedtheimageof29−323previously.ApulsedsupersonicbeamwasgeneratedbyC(P0)atthelongestwavelengthof∼333nm(FigureS1),expandingamixtureof0.3%CSandHeintothesourcesuggestingthethermochemicalthresholdofC(3P)+S202chamberwhereitwasskimmedbeforeenteringand(X3Σ−)channelshouldbelowerthan7.45eV(166.5nm).g845https://dx.doi.org/10.1021/acs.jpclett.0c03386J.Phys.Chem.Lett.2021,12,844−849

2TheJournalofPhysicalChemistryLetterspubs.acs.org/JPCLLetterspin−orbitinteractionplaysaminorroleinthisdissociationchannel.Inordertoabstractmoreinformation,aqualitativesimulationoftheenergydistributionwascarriedout.TheresultsofthesimulationrevealthattherotationaldistributionsofS(X3Σ−)arenarrowandappeartopeakatalowJatallof2gtheinvestigatedwavelengths.ThiscoldproductrotationaltemperatureindicatesthatthebendingmotionoftheCS2moleculeisnotextensivelyexcitedalongthedissociationcoordinate,andthedissociatingCS2moleculeprobablypossessesanearlineargeometry.Figure3showstherelativeFigure3.RelativepopulationofdifferentvibrationalstatesoftheS2(X3Σ−)andS(a1Δ)coproductsfromtheC(3P)detectionatfiveg2g1photolysiswavelengths.vibrationalstatepopulationsofSproducts.TheS(X3Σ−)22gproductsareobviouslyhighlyvibrationallyexcited,withthelargestpopulationatv=2,4,5,7,and5forthephotolysiswavelengths300.0,303.8,307.3,312.9,and320.0nm,respectively.ItisnotedthattheS(X3Σ−)productsshow2gquitesimilardistributionsatallfivephotolysiswavelengths,suggestingasimilardissociationmechanisminthiswavelengthregion.ThepopulationoftheS(a1Δ)productsissmallanda2glittlearbitrary,sincethereisnoclearsigntoseparatetheTKERspectraofS(X3Σ−)andS(a1Δ)products.2g2gTheproductspatialangulardistributionwasalsoobtainedbythefollowingequationf()θσβ={+1PP(cos)θβ+(cos)θ}(2)2244whereσistheproducttranslationalenergydistribution,β2andβ4areanisotropyparametersthatdependonthephoto-dissociationratesfortheformationofspecificphotofragmentsandthegeometryoftheexcitedmolecule,P2andP4arethesecond-andfourth-orderLegendrepolynomials,andθistheFigure2.Ionimagesandtranslationalenergydistributions(arb.scatteringangle.Theoverallangularparameterswereunits)ofC(3P)productsfromtwo-photondissociationofCSat12determinedbyfittingtheangulardistributionsinFigure2.wavelengthsof(a)300.0,(b)303.8,(c)307.3,(d)312.9,and(e)3320.0nm.TheringsshownintheimagescorrespondtotheTable1liststheoverallanisotropyparametersofC(P1)vibrationalstateoftheS(X3Σ−)andS(a1Δ)coproducts.productsatthefivephotolysiswavelengths.Theaveragedβ22g2gvaluesovertheproducttranslationalenergydistributionare∼0.2forC(3P)productsatthefivewavelengths,whiletheFigure2displaystheTKERdistributionsoftheC(3P)11channelbyintegratingoverallproductangles.Theinternal3−Table1.AnisotropyParameterValuesDerivedfromenergydistributionsofS2(XΣg)coproductscanbeobtained3fromtheTKERspectrabyusingthelawofenergySimulationsofDifferentialCrossSectionsforC(P1)PhotoproductsbyUsingEq2conservation.TheenergycombsrepresentingthevibrationalquantumnumbersofS(X3Σ−)productsarelabeledinFigure2g2.SincethefirstelectronicallyexcitedstateofS(a1Δ)iswavelengths/nmβ2β42gestimatedtobe∼4700cm−1higherthanthegroundstate,37300.00.23−0.01thevibrationalprogressionsofS(a1Δ)productsarealso303.80.23−0.022gdisplayedinFigure2.WehavealsoacquiredC(3P)imagesfor307.30.20−0.02Jthethreespin−orbitstates(J=0,1,and2)(FigureS2),which312.90.18−0.04showalmostthesamedistributions.Thisimpliesthatthe320.00.12−0.02846https://dx.doi.org/10.1021/acs.jpclett.0c03386J.Phys.Chem.Lett.2021,12,844−849

3TheJournalofPhysicalChemistryLetterspubs.acs.org/JPCLLetterFigure4.Ionimagesandtranslationalenergydistributions(arb.units)ofC(3P)productsfromone-photondissociationofCSbyusingtheVUV12FELlaseratwavelengthsof(a)127.9,(b)134.2,(c)137.3,(d)140.1,(e)141.0,and(f)143.9nm.TheringsshownintheimagescorrespondtothevibrationalstateoftheS(X3Σ−),S(a1Δ),andS(b1Σ+)coproducts.2g2g2gaveragedβ4valuesareclosetozero.AccordingtopreviouspartiallyresolvedstructuresintheTKERspectraatthesestudies,theabsorptionbandintheregionof290−330nmofwavelengthsillustratethatbothchannelsarehighlyvibration-CShasbeenassignedasaV-band,correspondingtothe1Ballyexcited.Nosuchfeatureshavebeenfoundforthehigher22(1Δ)←X1Σ+transition.38,39This1BstatehasaquitelongchannelsC(3P)+S(b1Σ+).Thereareseveralpronouncedug212glifetime;thus,theangulardistributionisdeterminedsolelybyintheTKERthatareinverygoodagreementwiththeenergythesecondtransitionfromtheintermediate1BstatetotheleveloftheS(b)state.Therefore,theS(b)channelshould222finalstate,andthecoherencebetweenthefirstandthesecondplayaroleinthedissociation.However,sincetheS2(b)state40photonswouldnotbeimportant.Fromourpreviouspaper,hassomeenergyoverlapwithotherstates,andtheTKERtwo-photonexcitationofCS2around300nmshouldbeviathespectradropsdramaticallyatverylowkineticenergy,thesequentialtransition1B(21Σ+)←1B(1Δ)←X1Σ+,asintensitiesofS(b1Σ+)productsshouldbeverysmall.22u2gdisplayedinFigure1.TheparalleltransitioninthesecondstepTheangulardistributionshavebeenextractedfromthehasledtoaβvalueofaround0.6−0.7fortheCS(X1Σ+)imagesbyintegratingtheintensityoverthecorresponding2g353productsbetween300and320nm.Incontrast,theβ2valueradicalrange.TheC(P1)ionimagesrevealslightlyismuchsmaller(∼0.2)fortheS(X3Σ−)coproducts,perpendiculardistributionswithaverageparametersaround2gsuggestingamuchslowerdissociationprocessforthelatter.−0.1to−0.3atthesixphotolysiswavelengths.TherelativelyThisisrational,becausethemoleculeneedstoundergothesmallvaluesshowveryweakanisotropicdistribution,isomerizationfromtheCS2tolinear-CSSandthendissociates.indicatingthatthisdissociationprocessshouldbequiteslow,Toexploremoreaboutthedissociationmechanism,wehavewhichissimilartothatobservedinthetwo-photonUV28alsoperformedone-photonexcitationofCS2byusingtheexcitationexperiments.TheoreticalcalculationspointedoutVUVFELlaserinthewavelengthregionof128−144nm.thatthe1B(21Σ+)stateofCSshouldplayamajorroleinthe22Figure4displaystheC(3P)ionimagesfollowingCSisomerizationandphotodissociationprocessesoccurringat12photodissociationat127.9,134.2,137.3,140.1,141.0,andhighenergies.Absorptionofonephotonwithhv≥7.08eV143.9nm,respectively.Eachimagewasobtainedbyshouldefficientlypopulatethe1B(21Σ+)state,sincethe2accumulatingtheC+signalsover30000lasershotswithtransitiondipolemomentoftheSCS1B(21Σ+)←X1Σ+is2backgroundsubtraction.Theredverticalarrowindicatestherelativelylarge.Inthiswork,CS2moleculesareexcitedeitherpolarizationdirectionoftheVUVFELlaser.TheTKERdirectlyto1B(21Σ+)stateortoevenhigherelectronicstates2distributionsderivedfromtheseimagesarealsoshowninfollowinginternalconversiontothe1B(21Σ+)stateby2Figure4.TheTKERspectracontainsmultipledissociationabsorbingtwophotons(300−320nm)oronephoton(128−channels,namely,C(3P)+S(X3Σ−),C(3P)+S(a1Δ),144nm).AsshowninFigure3andFigure5ainref28,the12g12gandC(3P)+S(b1Σ+).TheenergyresolutionoftheTKERpotentialof1B(21Σ+)stateisshallowandflatalongtheCS12g2spectraisnothighenoughtoclearlyseparatethedissociationdistanceandbendingangle,andamoleculeonthissurfacewillpathwaystothedifferentelectronicstatesofS2.Themaybeundergolarge-amplitudemotions,whichleadtoseveralduetomultipleproductchannelsortherelativelyhigherprocessesincompetition.Forinstance,the1B(21Σ+)state2rotationalexcitationoftheSproducts.Nevertheless,fromtheiscrossedbythe11Πstateforthelinearconfiguration(with2sharpstepsatthehighenergyonsetoftheS(a1Δ)products,energiesof∼7eV).AfterUVabsorption,theS(1D)+CS2gitisrationaltopointoutthattheproductionofC(3P)+S(X1Σ+)productscanbeformedthroughvibroniccoupling12g(a1Δ)competeswiththatofC(3P)+S(X3Σ−).Thewith11Π.Inaddition,S(3P)+CS(X1Σ+)productscanoccurg12gg847https://dx.doi.org/10.1021/acs.jpclett.0c03386J.Phys.Chem.Lett.2021,12,844−849

4TheJournalofPhysicalChemistryLetterspubs.acs.org/JPCLLetterafterspin−orbitcouplingwiththe3Πelectronicstates.ForZijieLuo−StateKeyLaboratoryofMolecularReactionbentstructures,the1B(21Σ+)stateiscrossedbythebentDynamics,DalianInstituteofChemicalPhysics,Chinese2componentofthe1A(11Π)state.TheCSSisomercanbeAcademyofSciences,Dalian116023,China1formedaftervibroniccouplingwith1A(11Π)statefollowedYaoChang−StateKeyLaboratoryofMolecularReaction1byanavoidedcrossingwiththegroundstateat115°.Finally,Dynamics,DalianInstituteofChemicalPhysics,ChineseCSScoulddissociatetoC(3P)+S(X3Σ−)throughabarrierAcademyofSciences,Dalian116023,China12gwithoutcouplingtoanotherelectronicstate.WhilehigherGongkuiCheng−StateKeyLaboratoryofMolecularelectronicstatesshouldbeinvolvedintheS(a1Δ/b1Σ+)ReactionDynamics,DalianInstituteofChemicalPhysics,2ggchannels,thedetailedpotentialenergysurfaceinformationChineseAcademyofSciences,Dalian116023,Chinaawaitsfurthertheoreticalinvestigations.OurexperimentshereJiayueYang−StateKeyLaboratoryofMolecularReactionclearlyidentifythattheS2moleculecanbeadaughterofCS2Dynamics,DalianInstituteofChemicalPhysics,Chineseinastrophysicalmedia.TheformationofS2fromtheCS2byAcademyofSciences,Dalian116023,Chinatwo-photonUVorone-photonVUVphotolysisisfollowedbyZhichaoChen−StateKeyLaboratoryofMolecularReactiondissociationmechanismsproposedbytheoreticalcalcula-Dynamics,DalianInstituteofChemicalPhysics,Chinesetions.28AcademyofSciences,Dalian116023,ChinaInsummary,wehaveinvestigatedthecentral-atomWeiqingZhang−StateKeyLaboratoryofMolecularReactioneliminationchannelofC+S2intheCS2photodissociationDynamics,DalianInstituteofChemicalPhysics,Chineseprocess.Inboththetwo-photonandone-photonexcitationAcademyofSciences,Dalian116023,Chinaexperiments,wehaveclearlyobservedtheS2productsinitsGuorongWu−StateKeyLaboratoryofMolecularReactiongroundstate(X3Σ−)andelectronicallyexcitedstates(a1Δ,Dynamics,DalianInstituteofChemicalPhysics,Chineseggb1Σ+).ThedissociationmechanisminvolvesphotoconversionAcademyofSciences,Dalian116023,China;orcid.org/gfromCS2tolinear-CSSandthendissociatesafterexcitationto0000-0002-0212-183Xthe1B(21Σ+)orhigherelectronicstates.GiventhesimilarityXuemingYang−StateKeyLaboratoryofMolecularReaction2ofOCS,CO2,andCS2,webelievethatthecentral-atomDynamics,DalianInstituteofChemicalPhysics,ChineseeliminationchannelismoregeneralthanexpectedintheAcademyofSciences,Dalian116023,China;DepartmentofphotodissociationoftriatomicmoleculesandshouldbeaddedChemistry,CollegeofScience,SouthernUniversityofScienceintothetextbookdissociationdynamicsmodels.andTechnology,Shenzhen518055,China;orcid.org/0000-0001-6684-9187■Completecontactinformationisavailableat:ASSOCIATEDCONTENThttps://pubs.acs.org/10.1021/acs.jpclett.0c03386*sıSupportingInformationTheSupportingInformationisavailablefreeofchargeatNoteshttps://pubs.acs.org/doi/10.1021/acs.jpclett.0c03386.Theauthorsdeclarenocompetingfinancialinterest.Additionalexperimentalresultsfortwo-photondissoci-ation(PDF)■ACKNOWLEDGMENTSTheexperimentalworkissupportedbytheChemicalDynamicsResearchCenter(GrantNo.21688102),the■AUTHORINFORMATIONNationalNaturalScienceFoundationofChina(NSFCNos.CorrespondingAuthors21873099,21922306,21590802),theKeyTechnologyTeamXinganWang−HefeiNationalLaboratoryforPhysicaloftheChineseAcademyofSciences(GrantNo.SciencesattheMicroscaleandDepartmentofChemicalGJJSTD20190002),theinternationalpartnershipprogramofPhysics,UniversityofScienceandTechnologyofChina,Hefei,ChineseAcademyofSciences(No.121421KYSB20170012),Anhui230026,P.R.China;orcid.org/0000-0002-1206-andtheStrategicPriorityResearchProgramoftheChinese7021;Email:xawang@ustc.edu.cnAcademyofSciences(GrantNo.XDB17000000).WethankKaijunYuan−StateKeyLaboratoryofMolecularReactionWentaoChenforhelpfuldiscussions.WealsothankthestaffDynamics,DalianInstituteofChemicalPhysics,ChineseteamoftheDalianCoherentLightSource(DCLS)forAcademyofSciences,Dalian116023,China;orcid.org/technicalsupport.0000-0002-5108-8984;Email:kjyuan@dicp.ac.cn■REFERENCESAuthors(1)Okabe,H.PhotochemistryofSmallMolecules;Wiley:NewYork,ZhenxingLi−HefeiNationalLaboratoryforPhysicalSciences1978.attheMicroscaleandDepartmentofChemicalPhysics,(2)Lu,Z.;Chang,Y.C.;Yin,Q.Z.;Ng,C.Y.;Jackson,W.M.UniversityofScienceandTechnologyofChina,Hefei,AnhuiEvidenceforDirectMolecularOxygenProductioninCO2Photo-230026,P.R.Chinadissociation.Science2014,346(6205),61−64.MinZhao−HefeiNationalLaboratoryforPhysicalSciences(3)Chen,W.T.;Zhang,L.;Yuan,D.F.;Chang,Y.;Yu,S.R.;Wang,attheMicroscaleandDepartmentofChemicalPhysics,S.W.;Wang,T.;Jiang,B.;Yuan,K.J.;Yang,X.M.;etal.ObservationoftheCarbonEliminationChannelinVacuumUltravioletPhoto-UniversityofScienceandTechnologyofChina,Hefei,AnhuidissociationofOCS.J.Phys.Chem.Lett.2019,10(17),4783−4787.230026,P.R.China(4)Tseng,D.C.;Poshusta,R.D.Ab-InitioPotentialEnergyCurvesTingXie−HefeiNationalLaboratoryforPhysicalSciencesatforLow-LyingStatesofCarbon-Disulfide.J.Chem.Phys.1994,100theMicroscaleandDepartmentofChemicalPhysics,(10),7481−7486.UniversityofScienceandTechnologyofChina,Hefei,Anhui(5)Zhang,Q.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