琥珀的激光拉曼光谱特征研究

采用激光拉曼光谱仪对波罗的海、多米尼加、缅甸三个地区的琥珀样品进行了拉曼光谱测试分析，描述了拉曼光谱的位置、形态、相对强度，分析了振动模式，同时对某些分子基团如ν（C-H），ν（C-O）做了谱带归属。结果表明，琥珀结构中碳链骨架振动是导致其拉曼光谱形成的主要原因，同一产地不同品种琥珀的拉曼谱峰特征基本一致，不同产地琥珀的拉曼谱峰仅在个别拉曼位移处存在较小差异。另外，对前人提出的用拉曼光谱中ν（C=C）和δ（CH2）的强度比值N（I1645cm-1／I 1450cm-1）来确定天然树脂成熟度的初步设想进行了验证分析。拉曼光谱对于琥珀真伪及其产地的鉴定有一定的辅助作用，但不能作为鉴别产地的唯一指示性依据。

Study on Raman Spectrum Characteristics of Amber

In recent years, authenticity identification and origin identification of ambers are becoming a hot topic in the academic research field. Scholars both at home and abroad make use of Fourier transform infrared spectroscopy （FTIR） to determine the amber authenticity and origin. Raman spectrum is considered to be a useful supplement of FTIR. The authors selectively collect different varieties of amber samples from three major producing areas in the world, the Baltic Sea, Dominica and Myanmar. With the help of laser Raman spectrome- ter, peak positions, peak shapes and relative strength characteristics of Raman spectra and their vibration patterns are described, mainly in the range of 3 200--400 cm i. Some molec- ular groups are analyzed such as vibration of C--H and C--O. The Raman spectra of amber samples from the same origin are compared and analyzed to find out their similar features, while the Raman spectra of amber samples from different origins are compared and analyzed to find out their discriminative features. The result clearly shows that the vibration of carbon chain frame in the molecular structure of amber is the main formation factor of Raman spec- trum. The features of peaks in the Raman spectra of different varieties of ambers from the same producing area are almost the same. The golden amber, foamy amber and cloudy amber from Baltic Sea have similar Raman spectrum. The Dominican golden amber has the sameRaman spectrum with the blue amber and the Raman spectra of golden amber, blood amber and brown red amber from Myanmar are consistent. The Raman spectra of ambers from dif- ferent producing areas only have slight differences in the Raman shift. Comparing with Ra- man spectra of ambers from the Baltic Sea, Myanmar and Dominica, Raman spectra of the Dominican ambers have some differences in the range of 1 700-1 400 cm-1 and the Raman shift of Burmese amber below 1 200 cm-1 has significantly fewer spectral peaks as well as less absorption intensity. The previous arguments and initial assumptions put forward that using intensity ratio of v（C=C） and δ（CH2） （N= 11 450 cm 1 /11 645 em 1 ） could determine the natural maturity of resin. The authors confirm that the value of N can react the change of the relative quantity of unsaturated carbon functional groups and saturated carbon functional groups in the amber internal structure as well as detect the status of the crosslinking poly- merization. However, the value of N could not be the only indicative evidence for origin i- dentification, since the Burmese amber has a lower value of N, while the N values of the Baltic ambers and the Dominican ambers are close.