优、劣质淡水养殖珍珠的显微激光拉曼光谱特征

In Situ Resonance Raman Spectra for High and Poor Quality Freshwater Cultured Pearls

采用3个不同的激发波长λ=514、633和785 nm对淡水养殖珍珠进行了较为系统的原位拉曼光谱研究,结果表明:当λ变化时,所有珍珠中所探测到的无机物拉曼峰频率没有频率色散现象;进一步证实了优质珍珠主要由文石组成,劣质珍珠主要由六方碳钙石组成;低于700 cm-1的晶格振动峰随着激发波长的增大强度增强,且劣质珍珠拉曼光谱低频区峰数较多,其碳酸钙晶体择优取向能力较差,说明珍珠的质量和珍珠所含晶型有明显关系。

In situ resonance Raman spectra for Chinese freshwater pearls is collected and systematically analysed with three different excitation wave numbers at λ=514,633 and 785 nm.The results are：Raman spectra of inorganic pigments in pearls has no frequency dispersion phenomena.It is further confirmed that high quality pearls contain mainly aragonite,while poor quality pearls mainly contain vaterite.The spectra strength of lattice vibration under 700 cm-1 increases gradually with the increment of excitation wave numbers.More spectra are probed at low frequency in poor quality pearls shows that the vaterite crystal has a spectrum showing more disorder than aragonite.So the quality of pearls is closely associated with its calcium carbonate polymorphs.