资源描述：
《仪器分析英文原版教案(5)》由会员上传分享，免费在线阅读，更多相关内容在行业资料-天天文库。
1、IntroductiontoAtomicOpticalSpectroscopy(Chapter8)Sampleisatomized(atoms/ions)absorptionoremissionmeasuredEnergyLevelDiagramsEveryelementshasuniquesetofatomicorbitalsp,d,f...levelssplitbyspin-orbitcouplingSpin(s)andorbital(l)motioncreatemagneticfieldsthatperturbeachother(couple)iffields
2、parallel-slightlyhigherenergyiffieldsantiparallel-slightlylowerenergyNNNSvs.SSSNDefineSOcouplingbyJ(totalangularmomentum)J=L+S(L=ålS=ås)(positivevaluesonly)CEM333page7.1Example:selectron(l=0,s=+1/2or-1/2)J=0+1/2=1/2pelectron(l=1,s=+1/2or-1/2)J=1+1/2=3/2(higherenergy)or1-1/2=1/2(loweren
3、ergy)ElectronicTermSymbol2S+1LJLwrittenasletter(S,P,D...)insteadofnumber!212Li=1s2sL=0,S=±1/2S1/2212Li*=1s2pL=1,S=±1/2P3/2,1/2221Be=1s2sL=0,S=0S021131Be*=1s2s2pL=1,S=1,0P2,P0CEM333page7.2Fig8-1¥Similarpatternbetweenatomsbutdifferentspacing¥Spectrumofiondifferenttoatom¥Separationsmeasur
4、edinelectronvolts(eV)-19-191eV=1.602x10C´1V(J/C)=1.602x10J-1=96.484kJ×mol¥As#ofelectronsincreases,#oflevelsincreasesEmissionspectrabecomemorecomplexLi30lines,Cs645lines,Cr2277linesCEM333page7.3DesirenarrowlinesforaccurateidentificationBroadenedby(i)uncertaintyprinciple(ii)pressurebroad
5、ening(iii)Dopplereffect(iv)(electricandmagneticfields)Atomiclinewidths:(i)UncertaintyPrinciple:QuantummechanicalideastatesmustmeasureforsomeminimumtimetotelltwofrequenciesapartDt×DE³hD{t×Dn{³1minimumminimumtimefordetectablemeasurementdifferenceinfrequenciesShowsupinlifetimeofexcitedsta
6、te¥iflifetimeinfinitelylong,DEinfinitelynarrow¥iflifetimeshort,DEisbroadenedCEM333page7.4ExampleLifetimeofHg*=2x10-8s.Whatisuncertaintybroadeningfor254nmline?117Dt×Dn=1Dn===5x10HzDt-82x10s-1n=c×lDifferentiatingwrttofrequency-2dn=-cldldn»Dnanddl»Dl7-1-92Dn×l25x10s×(254x10m)-4Dl===1.1x10
7、c8-13x10m×ssometimescallednaturallinewidthCEM333page7.5(ii)Pressurebroadening:Collisionswithatoms/moleculestransferssmallquantitiesofvibrationalenergy(heat)-ill-definedgroundstateenergyEffectworseathighpressures¥Forlowpressurehollowcathodelamps(1-10torr)10-1-10-2¥ForhighpressureXelam
