自旋动力学-第一章.

SPINDYNAMICS核自旋的操控，演化，弛豫Historical核磁共振成像技术（MRI）2003,Lauterbur(化学家)&Mansfield(物理学家)NMR方法与蛋白结构测定技术1991,Ernst（Fourier变换，二维NMR）2002,Wüthrich等NMR的发现与实现1944,Rabi(气体，分子束）1952,Purcell&Bloch（凝聚态物质）物理学奖化学奖生理医学奖五次诺贝尔奖，三个里程碑核心方法技术创新1930’sRabiMolecularBeam（分子束）HistoricalOVENSlitSlitDetectorFrequencyGeneratorRabi分子束实验----测定旋磁比RabimolecularbeamexperimenttomeasurezThecoil：产生x方向射频（RF）磁场(goingintotheboard).B0（静磁场）ww000Bw共振条件：Whenthefrequencyreachesresonance,particlesnolongerreachthedetector.0zB正向梯度0zB反向Bz0(FeynmanLecturesonPhysics)1946Bloch,Hansen,Pachard(StanfordUniv.)(液体H2O)Purcell,Torrey,Pound(HarvardUniv.)(固体：ParaffinWax)1kg1949-1951ChemicalShiftJ-Coupling：结构解析1953FirstCommercialH.R.ProtonNMRSpectrometer（¥3-5百万）Chemistsgotthepointveryquickly,thankedthephysicists,andtookover.——MartinPackard1H谱1960’sDoubleResonancePFT-NMR(CooleyandTukey)脉冲FourierNMR，双共振1975-2DNMRH.R.NMRinSolidHighfieldNMR1985-BiologicalNMRSpinImagingNMR信号相对其它检测方式灵敏度低液体NMR实验：g---mg现代固体NMR实验：~10mg第一次固体1HNMR（1945,Purcell):1kg石蜡(CWNMR)NMR应用从物理到化学FTNMR灵敏度已经104倍提高!!TechniqueAuthorEnhancementFTNMRErnstandAnderson~10-102Bo(60→600MHz)Oxford,Bruker32CryoprobesPeterStyles2-4M0NMR面临的挑战NMR面临的挑战—仍然是提高灵敏度应用从化学走向生物和医学，简单到复杂体系生物、医学样品：复杂，量少，稳定性1H(H2O)image分子影像13C，15N，31P……X样品量多（NMR）、空间分辨低（MRI)600→1000MHz14.1T→23.5T,灵敏度提高~2倍!（20年）NMR面临的挑战—时间分辨率NMR谱/MRI时间分辨:ms脑功能3.ThePrinciplesofNuclearMagnetismA.Abragam,CarendonPress,19614.PrinciplesofNuclearMagneticResonanceinOneandTwoDimensionsR.R.Ernst,G.Bodenhausen,A.Wokaun,ClarendonPress,19922.PrinciplesofNuclearMagneticResonanceC.P.Slichter,19931.SpinChoreography:BasicStepsinHighResolutionNMRRayFreeman7.核磁共振波谱裘祖文，裴奉奎19898.核磁共振原理与实验方法高汉宾张振芳，20086.LECTURECOURSE:NMRSPECTROSCOPY？？？5.UnderstandingNMRSpectroscopyJamesKeeler,2002参考书ElectronicMagnetismClassicalangularmomentumQuantumangularmomentumElectronicMagnetismCharater1经典角动量ClassicalangularmomentumSpinAngularmomentum(electron)轨道角动量（Orbitalangularmomentum）LrVmP(linearmomentum)wILS自旋角动量Spinangularmomentum（I:转动惯量）Magneticmoment（磁矩）22wer=ISnnr2TenorbitLLmeorbit2memeg2？？SLS-eExperiment:g=2SL电子圆周运动：轨道磁矩---轨道角动量电子自旋运动：自旋磁矩---自旋角动量磁旋比（magnetogyricratio）旋磁比（gyromagneticratio）L磁矩角动量L电子00BμE221EJIEnergy外磁场中的磁矩经典力学MagneticmomentinmagneticField动能势能力zBzEfzzz0Force,TorqueandMotionBμGTorque（力矩）：平动转动TorqueLawofangularmomentum(动量矩定理)----运动方程0BμdtdGJμBγ-Bμγdtμd00JosephLarmor(1857-1942)BμGTorque（力矩）：Jμ运动方程Larmorprocession拉莫进动w0γBωGraphicalInterpretation1.Quantumangularmomentum(orbit)π2h/1)(JJLmJ=-J,-J+1,……J-1,J2J+1values(~10-34Js))1(212JJBJLIEAngularmomentumisquantized.大小量子化JZmL角动量沿某一轴(Z任意）投影量子化磁量子数mJ：azimuthal（magnetic)quantumnumber空间取向量子化)1(2JJmeJeEJBohrmagnetron磁矩量子化LL方向或方位？？动能BjeJZmmem2轨道磁矩最小单元L外磁场中的角动量、磁矩（量子力学）角动量量子数JSZSZL1)(SSLS21zSZmLBSSL3Uhlenbeck,Goudsmit,1925BsesSSmmemLZz2LS非经典物理，相对论量子力学(~10-34Js)~eeevmr~ve~137C(光速）Quantumangularmomentum(spin)BJeJmmemZ2Spin:Orbit:总自旋S=1/2Z投影Mz=1/2Stern—Gerlach实验(1922):高温下蒸发中性顺磁的银原子束，通过不均匀磁场，无Lorentz力银原子束经典随机取向磁铁zBzEfzzz0esSZBzmemL21Experiment:(LS)Z(1/2,-1/2)量子+经典SL但是不能确定LS方向!!!电子自旋性质（实验）Oncewehaveselectedapurecomponentalongthez-axis,itstaysinthatstate.Spin½particle(e.g.silveratoms)“Improved”Stern-GerlachExperimentBz0Bz0电子自旋性质（实验）一旦选择纯＋Ｚ分量，就保持该态“Improved”Stern-GerlachExperimentSpin½particle(e.g.silveratoms)Whateverhappenedalongthez-axisdoesn’tmatteranymoreifwelookalongthex-axis.Itisonceagainsplitinto2beams.outbackBx0Bz0X电子自旋性质（实验）Ｘ方向两个态0010m1-m0mZ00γBωhυΔEFormulaBohr;1mruleselectionE-EI1,I，1,II,mmBγEBγBμEBBBLL能级和约迁Energylevelsandtransitions2/1m2/1mSL跃迁选择定则（射频场作用下）Whatisspin?mIz)]1([2IIII),1,...,1,(IIIImWhenaparticleisinstate,wecanknowthez-component……andalsothemagnitudeatthesametime.mandIarequantumnumbers.ForagivenI(e.g.½),mcantakevaluesfrom–Ito+I.Thus,thereare2I+1states.Whatisspin?Spinisaquantummechanicalpropertyofmanyfundementalparticlesorcombinationsofparticles.Itiscalled“spin”becauseitisatypeofangularmomentumandisdescribedbyequationstreatingangularmomentum.Angularmomentumisavector.Ideally,wewouldliketobeabletodeterminethe3Dorientationandlengthofsuchavector.However,quantummechanicstellsusthatthatisimpossible.Wecanknowoneorientation(byconventionthez-axis)andthemagnitudesimultaneously,buttheotherorientationsarecompletelyunknown.Anotherwayofstatingthesamethingisthatthez-component(Iz)andthesquareofthemagnitude(I2)simultaneouslysatisfythesameeigenfunctions.ElectronicMagnetism(材料磁性）χ:magneticsusceptibilityjjijiBMAnisotropicij:TensorBM10μ0=4π×10−7Hm−1vacuumpermeability.(isotropic)并矢Scalar标量（数）：转动变换下不变Vector矢量：),,(321AAAATensor张量：ｉｉ，ｉｊ，ｉｋ，ｊｉ，ｊｊ，ｊｋ，ｋｉ，ｋｊ，ｋｋ二阶Tensor张量：９个分量（i,j=1,2,3)klklljkiijACCA'转动变换下:AA扩散系数，应力，应变……DCDC转动变换下:jjijiACA''A顺磁paramagnetic(χ0).1/TUnpairedelectron---Curielaw1/(T-Tc)Curie-Weisslaw:independentofT(Metal)T=0K2/31)(SSQuantumclassical抗磁diamagnetic(χ0,in