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红外吸收光谱的基本原理
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悠洋棋牌TIANJINSHINENGPUKEJIYOUXIANGONGSI

时间: 2018-12-29 浏览量: 1127

一、红外吸收光谱的产生

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表1 红外区的划分

区域σ/cm—1ν/μm能级跃迁类型
近红外区13300~40000.75~2.5分子化学键振动的倍频和组合频
中红外区4000~4002.5~2.5化学键振动的基频
远红外区400~1025~1000骨架振动、转动

红外吸收光谱的基本原理

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悠洋棋牌YOUJINGDIANLIXUEHUOLIANGZILIXUEJUNKETUICHUSHUANGYUANZIFENZIZHENDONGPINLV(Hz)DEJISUANGONGSHIWEI:


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用波数(cm—1)作单位时:

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悠洋棋牌SHIZHONG    kYIJIANDELICHANGSHU,dyn/cm;

           μ一折合质量(,m1和m2分别为两个原子的质量),g;

           c一光速


若力常数k单位用N/cm,折合质量μ采用原子质量单位m=1.65×10—24g,上式可简化为


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表1 化学键的伸缩振动力常数

WechatIMG188.jpeg



二、简正振动和振动类型

(一)简正振动

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图1 水分子与二氧化碳分子的简正振动模式



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红外光谱的吸收峰除基频峰外,还有倍峰和组合频峰。倍频峰是由基态(v=-0)跃迁到v=2,3…激发态引起的,一般一级倍频峰(v=2)的强度仅是基频峰的1/10~1/100。组合频峰是在两个以上基频峰波数之和(σ12+…)或差(σ1—σ2悠洋棋牌…)处出现的吸收峰,吸收强度比基频峰弱得多。

红外吸收光谱的基本原理


(二)红外光谱中振动类型及其表示符号

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表2 各种振动形式的中、英文名称和符号

振动类型
英文名称符号
伸缩振动stretching vibrationν
     对称伸缩类型   symmetrical stretching vibrationνs
     不(或反)对称伸缩类型   asymmetrical stretching vibrationνas
变动振动(或弯曲振动)deformation vibration (bending vibration)δ
     对称变形振动    symmetrical deformation vibrationδs
     不(或反)对称变形振动    asymmetrical deformation vibrationδas
     面内弯曲振动    in-plane bending vibrationβ
     面外弯曲振动    out-of-plane bending vibrationγ
     卷曲振动    twisting vibrationτ
     平面摇摆振动    rocking vibrationρ
     非平面摇摆振动    wagging vibrationω


悠洋棋牌SHENSUOZHENDONGHEBIANXINGZHENDONGFANGSHI,RUTU2SUOSHI

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图2 伸缩振动和变形(弯曲)振动

+ 代表由纸面向外;— 代表由纸面向内



三、振动频率理论和振动谱带强度理论简介

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理论把光谱谱带的强度与分子中价键的特性相关联,能够给出键矩、键极化率以及这些量在分子振动时所产生的变化,并可预示光谱谱带的强度分布。该理论选用电光学参数来表示偶极矩对简正坐标的导数。由 Gribov等发展的光学光谱软件包可用简正坐标方法和强度的光-电参数法处理红外和拉曼光谱数据,给出计算频率、势能分布、振动归属以及分子键矩和键极化率张量对简正振动坐标的导数,生成分子碎片库数据,也能用来解反向电光学参数问题,以及用于生成预示光谱图。

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