天然与人工辐射绿色钻石中晶格辐射损伤的差异性及其光谱学表征

Difference of Lattice Radiation Damage and Spectroscopic Characterization in Natural and Artificial Radiation Green Diamonds

  • 摘要: 基于绿色金刚石的人工辐射实验研究结果,针对近年来面市的天然与人工辐射绿色钻石在检测过程中面临的难点问题,采用激光拉曼光谱仪、紫外-可见光谱仪、光致发光谱仪、红外光谱仪等光谱学测试方法,拟就天然与人工辐射绿色金刚石样品的宝石学和光谱学特征进行测试与分析。结果表明,以吸附态形式附着在金刚石表面的次生铀矿物为天然辐射源,由其238U同位素链上原子核自发衰变过程中释放出α射线是导致金刚石表面绿色辐射斑点或绿色薄壳形成的主要缘由。金刚石表面绿色辐射斑点由外向内随着晶格辐射损伤程度的增强,其蜕晶化程度依次递增直至趋于非晶态。与此相对应,由其表面绿色辐射斑点内晶格振动导致的1 332 cm-1附近拉曼峰强度自外向内依次递减,直至湮灭。反之,1 625 cm-1附近拉曼峰强度及其半高宽值自外向内依次递增。鉴于天然与人工辐射源产生的放射性强度与辐射剂量的差异性,故在金刚石中诱生的GR1心浓度及与之对应的光谱学特征亦有所不同。依据绿色钻石中GR1心(741nm) PL峰的分裂程度和半高宽,UV-Vis光谱中GR1心的ZPL、声子伴线(边带)和电子-声子耦合谱带的组合特征,并配合由H1a、H1b、H1c心振动导致的1 450、4 936、5 165 cm-1附近特征红外吸收峰等综合检测参数有助于区分天然与人工辐射处理绿色钻石。

     

    Abstract: Based on the experimental results of artificial radiation of green diamonds, with respect to the difficulties in detecting green diamonds under artificial and natural radiation in the market in recent years, the gemmological and spectroscopic characteristics of green diamond after natural and artificial radiation were tested and analyzed by using laser Raman spectrometer, ultraviolet-visible spectrometer, photoluminescence spectrometer, infrared spectrometer, and other spectroscopic test methods. According to the results, the absorbed secondary uranium minerals attached to the diamond surface is a natural radiation source, and the α-rays emitted during the spontaneous decay process of atomic nuclei on 238U isotope chains are the main factors causing the formation of green radiation spots or green thin shells on the surface of green diamonds. As the radiation damages of lattice increase, the degree of metamictization of the green radiation spots on the surface of the green diamond samples continue to increase progressively until it tends to be amorphous state from outside inwards. Correspondingly, the intensity of the Raman peak near 1 332 cm-1, that is caused by the lattice vibration in the surface green radiation spots, decreases sequentially from outside inwards until annihilation. Conversely, the intensity of the Raman peak near 1 625 cm-1 and its half-height width increase sequentially from outside inwards. In view of the difference between the radioactive intensity and the radiation dose produced by natural and artificial radiation sources, the concentration of GR1 center induced in diamond and its corresponding spectroscopic properties also differ to some extent. Corresponding to the splitting degree and half-height width of the PL peak at the GR1 center (741 nm) of green diamond, the combined properties of ZPL, phonon replica(sideband) and electron-phonon coupled bands of GR1 center in the UV-Vis spectrum, and the characteristic infrared absorption peaks near 1 450, 4 936 cm-1, and 5 165 cm-1 caused by H1a, H1b, and H1c center vibrations, are helpful to distinguish green diamonds treated by natural or artificial radiation.

     

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