近红外光谱分析技术在宝石研究中的应用

Application of Near Infrared Spectroscopy in the Study of Gems

运用傅里叶变换红外光谱仪对常见宝石、玉石、有机宝石的近红外光谱进行分析研究以及谱峰归属。宝石的近红外光谱表明,宝石矿物中广泛存在不同类型水的合频、倍频吸收峰,也可出现能量较低的电子跃迁吸收峰,其中水分子组合频吸收峰位于5 200cm-1±,OH的倍频吸收峰位于7 000cm-1±,以5 898cm-1±和7 849cm-1±为中心的强宽吸收谱带为能量较低的电子跃迁吸收峰,并且当只有7 000cm-1±出现时表明水以—OH的形式存在于宝石中,当5 200和7 000cm-1±吸收峰同时存在则表明宝石矿物中水的存在形式既有水分子也有—OH。而有机宝石近红外光谱以7 000cm-1±NH伸缩振动的一级倍频和5 200cm-1±NH伸缩振动与酰胺Ⅱ的组合频为特征。但是,近红外光谱吸收峰的峰位、峰型、相对强度因有机宝石的品种不同而有所区别。苯环中CH的伸缩振动与弯曲振动组合频吸收峰(4 061和4 179cm-1±)、CH伸缩振动与苯环骨架振动的组合频吸收峰(4 621和4 683cm-1±)为经过有机物充填处理的宝玉石的特征谱峰,其中,与苯环有关的吸收峰,表示样品经过充填处理,指示样品中环氧树脂的存在。

At present ,the application of infrared spectroscopy in the study of gem identification has been more concentrated in the mid-infrared range of 400~4000 cm-1 ,and related research on the near-infrared region of the spectrum 4000~10000 cm -1 has been rarely done .This paperstudied the gemstones ,jades and organic gems＇ NIR spectroscopy by Fourier transform infrared spectrometer .The results showed that gem mineral＇s NIR widespread presence of water absorption peak ,whichwas mainly for different types of water combination tone and overtone ,also can appear lower-energy electronic transition absorption peaks . 5200 cm-1 ± was a combination tone of water molecules ,and 7000 cm -1 ± was a overtone of —OH while 5898 and 7849 cm -1 ± centered strong broad absorption band was a lower-energy electronic transition absorption peak .When there was only 7000 cm-1 ± absorption peak ,description that water in gem mineral only existed in the form of —OH .When there were 5200 and 7000 cm -1 ± absorption peaks at the same time ,description that water existed in the form of molecules and —OH .The characteristics of organic gems were 5200 cm -1 ± for the combination tone of NH stretching vibration and amide II and 7000 cm -1 ± for the first overtone of NH stretching vibration .The near-infrared spectrum absorption peaks of different varieties of organic gems had different characteristics of position ,shape and the relation strength .The characteristics of organic filling gems were 4061 ,4683 cm-1 ± for the combination tone of benzene ring＇s CH stretching vibration and bending vibration and 4620 ,4683 cm -1 ± for the combination tone of CH stretching vibration and benzene ring skeleton vibration .The absorption peak associated with benzene ring ,generally indicates that the sample through the fill process .