仪器分析英文原版教案（0）

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1、IntroductiontoSpectroscopy(Chapter6)Electromagneticradiation(wave)description:WavelengthlVelocityvAmplitudeA0ElectricFieldStrengthTimetorDistancexPeriodptimefor1ltopassfixedpointæ1öFrequencyn#oflpassingpersçn=÷èpøæ1öWavenumbern#oflpercmn=èløVelocityvDistancepointonwavetravelspersecondv

2、=n×lInavacuum:vvacuum=c=2.99782x108m/sAsetofwaveswithidentical(a)freqency(b)phasearecalledcoherent.CEM333page2.1Frequencyisalwaysfixedbutvelocitycanvary!Wavesslowdowninmedium(gas,liquid,solid)sov

3、pnelectricfieldfrequencyamplitudephaseangularfrequencytimeWavedescriptionexplainscertainEMradiationphenomena:transmissionreflectionandrefractiondiffractioninterferencescatteringpolarizationCEM333page2.2ParticleDescriptionofLight:BasedonquantummechanicshcEnergyofEMphoton:E=hu=lPlanck'sC

4、onstant=6.626x10-34JásPostulatesofQM:1.Atoms,ionsandmoleculesexistindiscreteenergystatesonlyE0=groundstateE1,E2,E3...=excitedstatesExcitationcanbeelectronic,vibrationalorrotationalEnergylevelsforatoms,ionsormoleculesdifferent.Measuringenergylevelsgivesmeansofidentification-spectroscopy

5、2.Whenanatom,ionormoleculechangesenergystate,itabsorbsoremitsenergyequaltotheenergydifferenceDE=E1-E03.ThewavelengthorfrequencyofradiationabsorbedoremittedduringatransitionproportionaltoDEh×cDE=h×n=lCEM333page2.3EmissionSpectraPlotofemissionintensityvs.norlcalledemissionspectrumAtom:At

6、omicAtomicExcitationEmissionE2Lifetime~1-100nsE1DE=362.5kJ/molEnergyDE=202.8kJ/mol1414n=9.08x10Hzn=5.08x10Hzl=330nml=590nmE0lineemissionspectraInnershell(core)electrons(1s¬2p)-x-raysphotonsOutershell(valence)electrons(3d¬4p)-UV/visphotonsMolecule:MolecularMolecularExcitationEmissionE2E

7、R101R0EnergyV3V2LifetimeEV11-100fs0Band1Band2V0vibrationalandrotationaltransitions-bandemissionspectraCEM333page2.4Emissionspectrumofbrine(Fig.6-15):CEM333page2.5BallparkEnergyLevelSpacings:DE(Electronic)>100MJ/mol(x-ray)to<100kJ/mol(UV-vis)DE(Vibrational)<1to<100kJ/mol(IR)DE(Rotatio