第七章 红外和拉曼光谱.ppt

单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,第七章 红外和拉曼光谱法,概述,原理,红外光谱仪器,样品处理,分析应用,拉曼光谱简介,第七章 红外和拉曼光谱法,BACK,一.概述,红外,吸收,分子中结构和电子分布,拉曼,光散射,分子中结构和电子分布,BACK,二.基本原理,红外光谱,红外吸收,分子振动类型,伸缩振动的机械类型,复杂分子的振动,基团特征频率和峰强度的影响因素,BACK,2-1 红外光谱,红外区,波长,m,波数,cm,-1,对应能级,近,0.78-2.5,12800-4000,弱电子跃迁,中,2.5-50,4000-200,分子振动,远,50-1000,200-10,分子转动,常用,2.5-15,4000-670,分子振动、转动,BACK,红外光谱图,BACK,2-2,红外吸收,IR,区主要限于分子各振动和转动能态间的跃迁,分子必须有一个由振动或转动引起的偶极矩的净变化：,辐射频率与分子振动的自然频率相匹配；,BACK,红外振动的类型,Energy in molecules is quantised.,In,i.r,.,molecules are exposed to radiation between 10,14,Hz 10,13,Hz(wavelengths 2.5,m-15 m).Remember:c=,v,Bonds vibrate and stretch(pull apart then push together again)as they absorb energy.,CO,2,的振动,Asymmetric stretch,Symmetric stretch,bending,2-3 分子振动类型,molecular dipole moment must change during a vibration to be IR active.,this oscillating dipole interacts with the oscillating E-M field of the photon,leading to absorption.,+,+,+,Stretching Vibrations,Bending Vibrations,symmetric,anti-symmetric,rocking,scissoring,twisting,wagging,In-Plane,Out-of-Plane,Changes in bond length,Changes in bond angle,伸缩,：对称,非对称,弯曲,：摇动 剪切 扭动 摆动,三原子分子的振动,甲烷碎片分子的振动,CH,4,振动,2-4 伸缩振动的机械类型,双原子分子振动,振动的量子化,非谐振子,BACK,1.双原子分子振动,BACK,简 谐 振 动,2.振动的量子化,BACK,双原子分子的核间距与位能,谐振子,3.非谐振子,BACK,2-5 复杂分子的振动,分子具有3,N,个自由度,整个分子平动 3,整个分子转动 3,故分子内原子间运动（振动）为 3,N-3-3,线性分子转动自由度为2，振动为3,N-3-2,振动处理的条件：,分子质心在空间位置不变且不能转动；,所有质点运动是同相运动。,BACK,醇羟基的振动,2-6 基团特征频率和 峰强度的影响因素,内部因素,外部因素,BACK,1.内部因素,诱导效应,中介效应,共轭效应,氢键,振动偶合,BACK,2.外部因素,物质存在形式,溶剂效应,BACK,三红外光谱仪器,红外光源,单色仪,检测器,红外分光光度计,BACK,3-1 红外光源,Nernst,灯,碳化硅棒,BACK,Infrared Sources-,能斯特灯,The Nernst Glower or Nernst Lamp.An early light bulb which did not need to operate in vacuum like Edisons W filament bulb.A ZrO,2,:Y,2,O,3,:Er,2,O,3,(90:7:3)mixed oxide.A current passing through it would heat it to glowing.Needed an external filament to get it hot to begin,but then it could continue on its own.,Gives a good spectrum from 1 to 10 m;intensity varies 3 orders of magnitude,Infrared Sources-2,The,Globar,is a competitor of the Nernst Glower.Similar concept,but uses SiC instead of metal oxides.Can start heating from room temperature.,Globar,is a bit better for wavelengths below 5 m;also the,Globar,requires water cooling of the filament supports.,SiC,棒,Infrared Sources-3,Incandescent wire sources are longer lasting but lower intensity than the glower or,globar,.A,nichrome,wire or rhodium wire heated to around 1100 K is a good IR source.,特种灯泡 镍铬，铑丝,A tungsten filament lamp can also work as a good source in the near-IR region.,Infared,Sources-4,The most difficult spectral region in which to function is the Far-IR.Few sources are available.The mercury arc lamp does provide some Far-IR radiation and has been used as a source for this type of experimentation.,Infrared Sources-5,Most exciting is a new source coming on-line:the Canadian Light Source(CLS)is a synchrotron being built at the University of Saskatchewan.It is an extremely bright source of light and has,by comparison,a lot of light in the FarIR.Experiments never before possible are being planned.,Also have projects using mid-IR to do spectromicroscopy-spectroscopy with spatial microscopic resolution.One project focusing especially on biological samples,doing IR work on a single cell.,3-2 单色仪,可用棱镜、光栅、滤光片等,IR,能量低，要紧可能避免能量损失,BACK,3-3 检测器,目前使用的有两大类：,光子检测器,热检测器,BACK,热检测器,热电偶,Galay,池,热敏电阻,Galay,池,GALAY,池（,a),GALAY,池(,b),热敏电阻,热电检测器,BACK,3-4 红外分光光度计,色散型红外分光光度计,FTIR,BACK,红外分光光度计,1.色散型红外分光光度计,BACK,2.,FTIR,光谱仪,核心：,Michelson,干涉仪,Michelson,干涉,FT-IR,光谱仪,The Interferometer,Fixed Mirror,Moving Mirror,Laser,White Light,IR Source,Beam Splitters,IR Detector,Laser Detector,White Light Detector,Linear Drive Motor,单色光源照明的,Michelson,干涉仪,2.,FTIR(Fourier Transform IR),BACK,波的迭加,FTIR,中时间域的函数,时间域和强度,FTIR,的优点,同时测量所有的辐射，使时间大大缩短；,通过装有激光校正的干涉仪，可得到高分辨率,三维,FT-IR,谱,四样品处理,红外透明材料,KBr,NaCl,CaF,2,等,BACK,四样品处理,气体,液体和溶液,固体,BACK,4-1 气体,BACK,4-2 液体池,IR transparent Salt Plates,红外样品池,红外样品池,Slide 9,红外样品池加样,红外样品池,红外样品池,测量,Light Path,(shown by red line),4-3 固体,压片法,内反射法,BACK,内反射法,五分析应用,定性分析,定量分析,BACK,红外光谱图,氯仿的红外光谱图,典型的红外光谱图,5-2 定量分析,峰高法,基线法,BACK,2.基线法,苯的红外光谱,苯衍生物的红外光谱,应用举例,六.拉曼光谱简介,概述,原理,Raman,仪器,与,IR,比较,BACK,Raman,原理,瑞利和拉曼散射,Raman,Raman,散射的去偏振度,Raman,活性,6-3,Raman,仪器,光源,样品照射系统,分光光度计,样品照射系统,分光光度计,FT-Raman,光谱仪,6-4 与,IR,比较,样品处理,仪器,1.样品处理,玻璃池代替卤化物,IR,池；,溶解度小的可研成粉末，不用象,IR,研磨至糊状；,聚合物亦无需处理；,重要的是水无影响，生物体系、无机物、水污染直接测定；,有胶体或浮物使光束散射，不能观察,Raman,效应。,2.仪器,光学元件：玻璃即可，对中、远、红外（4000-25,cm,-1,）,用同一套系统观测,Raman,光谱；,IR,则要换光栅，但,Raman,光栅质量要求高；,检测器,PMT,即可，灵敏度，速度高于热检测器；,分辨本领：差不多；,价格：目前没有较便宜的,Raman,光度计。,Raman,与,IR,谱比较,Spectra of PETN explosive.,From D.N.,Batchelder,Univ.of Leeds,ATR,活体实时分析,本章要点,红外光谱的原理,计算,红外光谱振动的类型，活性,红外光谱的影响因素,红外光谱仪，扫描,/FTIR,，干涉仪,拉曼光谱，与红外光谱的比较,尾号,0,，,1,，,3,，,5,同学的读书报告,红外遥感原理与应用,最后日期：5月24日,