分子光谱学 第六章 振动光谱学

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1、Chapter6VibrationalspectroscopyCollegeofPhysics,QufuNormalUniversityZhangshu-dong2011-4-156.1DiatomicmoleculesHarmonicoscillatorEnergylevels:Termvalues:Forceconstantk:Potantialenergy:kisnotaffectedbyisotopicsubstitution!Hooke’slawUnitsofk:Nm-1,mdynA-1,aJA-2Q:Whatisbondorder?

2、6.1.1InfraredspectraTransitionmoment:Forhomonucleardiatomicmolecules:Forheteronucleardiatomicmolecules:---SelectionruleBand,fundamentalband,firstovertoneband,hotband,…Thev=1-0bandInfraredspectrumofDCl.BandandlinesQ:Whatdoestheintensitydependon?6.1.2RamanspectraTransitionmoment

3、:Forhomonuclearandheteronucleardiatomicmolecules:---SelectionruleBoltzmanndistributionlaw:Q:Theintensityofanti-StokeslineisusuallyweakerthanthatofStokesline,why?6.1.3AnharmonicityMorsepotentialDe:dissociationenergyb:potentialparameter,curvatureTermvalues:Birge-Sponerplot:Hint:

4、tosolvetheareaunderthelineWorkedexample6.16.1.4vibration-rotationspectroscopyTermvalues:InfraredspectraSelectionrules:---branchTherotationtransitionsmaybeobservedonlyinthegasphaseatlowpressureandusuallyinanabsorptionprocess.InfraredspectraTransitions:InfraredspectraZerogap:Inf

5、raredspectraCombinationdifference:ThelowerstatecombinationdifferencesTheupperstatecombinationdifferencesExercises6.1hintsRamanspectraSelectionrules:---branchRamanspectraTransitions:RamanspectraCombinationdifference:ThelowerstatecombinationdifferencesTheupperstatecombinationdif

6、ferencesJJ+2J-2O(J+2)S(J-2)JJ+2J-2O(J)S(J)6.2PolyatomicmoleculesSomekindsofvibrationalpatternsCommonsymbolsforvibarion6.2PolyatomicmoleculesNormalmodesofN-atommoleculesLinearmolecules:3N-5Non-linearmolecules:3N-6Q:Howtodetermineandtoclassifythenormalmodessymmetry,infraredactiv

7、ity?6.2.1GroupvibrationsandskeletalvibrationsTermvaluesforithnormalmodes---harmonicapproximationFornon-degeneratedmodes:Fordegeneratedmodes:Totalvalues:6.2.1GroupvibrationsandskeletalvibrationsFundamental,overtone,andcombinationtoneSelectionrule:6.2.1Groupvibrationsandskeletal

8、vibrationsGroupvibrations:onegroupinamoleculewhichmovementism