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 Far-IR.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,