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1、CoherentControlCoherentControlattemptstocontrolachemicalreactionwithlight,usuallyacleverlyshapedultrashortlaserpulse.Whyit’shard:IVR.Usingshapedpulsesandaniterativeapproach.Wave-functionPotentialC=catalystConventionalmethodsofchemicalcontrolMuchcanbedone,butnoteverythingwe’dlike.Coher
2、entControlChemicalreactionsproceedinamannerdeterminedbythemolecularHamiltonian.Whatifwe’dliketochangethisandmakedifferentproducts?Bringinalightfrequencytoexciteabondwe’dliketobreak.Butit’snotsoeasy!There’salotmoretoit.Along-helddreamofchemists.It’snowcomingtrue.Shapedultrashortpulses
3、arethekey.CoherentcontrolslidesmostlythankstoGustavGerber,UniversityofWurzberg,GermanyMargaretMurnaneandHenryKapteyn,JILARobertLevis,TempleUniversityIVRoccursonafew-fstimescale,solongpulsesexciteentiremolecule,andtheweakestbondbreaks,nomatterwhichbondwasexcited.ExciteonebondAfewfslate
4、r,however,theentiremoleculeisvibrating.IntramolecularVibrationalRedistributionThebondvibratesSingle-parametercontrolSurprisingly,thesesimplemethodsoftenwork,buttheyarenotgeneral.Coherentcontrol:UsingshapedultrashortpulsestocontrolthereactionCananultrashortpulsecauseamoleculetovibratein
5、suchawayastobreakthebondofourchoice?ThephysicsofcoherentcontrolMoleculeE-fieldofLaserPerturbedSystemWave-functionPotentialThepulseelectricfieldperturbsthemoleculeandpotentiallydissociatesit.Thetrickistocomputetherequiredpulseelectricfield.Wave-functionPotentialTryingtodothetheoryforcoh
6、erentcontrolHsystem=Hmolecule+Hradiation+HinteractionHradiationknownHmoleculesmallmolecules:approximatelargemolecules:unknownHinteractionweakfield:knownstrongfield:unknownFirst,weneedtoknowthecompleteHamiltonianforthemoleculeandradiation:Forallbutthesimplestmolecules,it’shopelesstosolv
7、etheproblem.Wecouldtrytosolvetheproblemtheoretically,butit’seasiertojustdoititerativelyinthelab.Pulse-shapingisimportantforcoherentcontrol.GeneticalgorithmforcoherentcontrolThisalgorithmwasdevelopedforcomputeroptimization,but,forcoherentcontrol,itcanbeimplementedaspartofanexperiment.