仪器分析 英文原版 教案 (1)

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1、OpticalSpectroscopyandInstrumentation(Chapter7)(IR,visibleandUV)pathlengthbconcentrationcI0IITransmittanceT=I0IPercentTransmittance%T=´100%I0AbsorbanceA=-logTI=-logI0I0=logIExamples:T=1.00(100%T),A=0.00T=0.10(10%T),A=1.00T=0.001(0.1%T),A=3.00CEM333page3.1Beer'sLaw:Basisforabsorbancespec

2、trophotometryAµcandAµbsoAµb×cA=a×b×cproportionalityconstantabsorptivity-unitsofL/gácmIfunitsofconcentrationareM(mol/L)thenusemolarabsorptivityeA=e×b×cunitsofL/molácmPhenomenausedforopticalmeasurements,(1)Absorption(2)Emission(3)Luminescence(Fluorescence,Phosphorescence,Chemiluminescence

3、(4)ScatteringInallcases,responseisproportionaltoconcentrationofanalyteCEM333page3.2Manyopticalinstrumentssharesimilardesign(1)stableradiationsource(2)transparentsampleholder(3)wavelengthselector(4)radiationdetector(5)signalprocessorandreadoutFig6-22CEM333page3.3RadiationSources:(Fig.7-3

4、)CEM333page3.4Continuumsourcesproducebroadrangeofl's(oftenblackbody)Heatedsolid(Globar,nichromewire)(1-40mm)Tungstenlamp(300-3000nm)QuartzTungstenHalogen(QTH)lamp(200-3000nm)hightemperature(3500K)EvaporationW(s)®W(g)W(g)+I2(g)®WI2(g)RedepositionWI2(g)+W(s)®W(s)+I2(g)D2lamporHg/Xearc-lam

5、p-(160-400nm)electronicexcitationD+E®D*®D(KE)+D(KE)+hn2electrical212KE1+KE2+hn=Eelectrical-BDEbonddissociationenergyCEM333page3.5LineSourcesproducefewdiscretewavelengthsD2lamporHg/Xearc-lamp(>400nm)Atomicemissionhollowcathodelamp(a)electronbombardmentofcathode(b)sputteringofcathodeatoms

6、(c)emissionfromelectronicallyexcitedcathodeatomsFig.9-11Electrodelessdischargelamps(EDL)(a)ArionscreatedbyRFenergy(b)ionscollidewithgaseousmetalatomswhichthen(c)emitexcite(Fig.9-12)CEM333page3.6LaserLightAmplificationbyStimulatedEmissionofRadiation(a)pumpingofexcitedstate(b)stimulatedem

7、issiontoproduceemission(Fig.7-5)CEM333page3.7PopulationInversionandAmplification:Fig7-6CEM333page3.8NeedpopulationinversionforlasingCannotproducepopulationinversionin2-levelsystem(stimulatedemissionbecomesincreasinglydominant).Need3-or4-levelsFig7-7Lasingmediumcanbesolid(Nd:YAG