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1、CoherentControlCoherentControlattemptstocontrolachemicalreactionwithlight,usuallyacleverlyshapedultrashortlaserpulse.Whyit’shard:IVR.Usingshapedpulsesand aniterativeapproach.Wave-functionPotentialC=catalystConventionalmethodsofchemicalcontrolMuchcanbedone,butnoteverythingwe’dlike.
2、CoherentControlChemicalreactionsproceed inamannerdeterminedby themolecularHamiltonian.Whatifwe’dliketochangethisandmakedifferentproducts?Bringinalightfrequencytoexciteabondwe’dliketobreak.Butit’snotsoeasy!There’salotmoretoit.Along-helddreamofchemists.It’snowcomingtrue.Shapedultras
3、hortpulsesarethekey.Coherentcontrolslidesmostlythanksto GustavGerber,UniversityofWurzberg,GermanyMargaretMurnaneandHenryKapteyn,JILARobertLevis,TempleUniversityIVRoccursonafew-fstimescale,solongpulsesexciteentiremolecule,andtheweakestbondbreaks,nomatterwhichbondwasexcited.Exciteon
4、ebondAfewfslater,however,theentiremoleculeisvibrating.IntramolecularVibrationalRedistributionThebondvibratesSingle-parametercontrolSurprisingly,thesesimplemethodsoftenwork,buttheyarenotgeneral.Coherentcontrol:UsingshapedultrashortpulsestocontrolthereactionCananultrashortpulsecause
5、amoleculetovibrateinsuchawayastobreakthebondofourchoice?ThephysicsofcoherentcontrolMoleculeE-fieldofLaserPerturbedSystemWave-functionPotentialThepulseelectricfieldperturbsthemoleculeandpotentiallydissociatesit.Thetrickistocomputetherequiredpulseelectricfield.Wave-functionPotential
6、TryingtodothetheoryforcoherentcontrolHsystem=Hmolecule+Hradiation+HinteractionHradiationknownHmoleculesmallmolecules:approximatelargemolecules:unknownHinteractionweakfield:knownstrongfield:unknownFirst,weneedtoknowthecompleteHamiltonianforthemoleculeandradiation:Forallbutthesimple
7、stmolecules,it’shopelesstosolvetheproblem.Wecouldtrytosolvetheproblemtheoretically,butit’seasiertojustdoititerativelyinthelab.Pulse-shapingisimportantforcoherentcontrol.GeneticalgorithmforcoherentcontrolThisalgorithmwasdevelopedforcomputeroptimization,but,forcoherentcontrol,itcanb
8、eimplementedaspartofanexperiment.
