改色处理紫红色钻石的光谱学特征及鉴定方法

以市场上销售的国内改色紫红色圆刻面型钻石为研究对象，通过对其光谱学特征进行分析，确定了此类紫红色改色处理钻石的鉴定。样品颜色呈现不同饱和度的紫红色，净水称重法测试比重为3.52，放大观察，样品DR-2与DR-3的部分刻面光泽较弱，显示了未被重新抛光的严重烧蚀区域，石墨化沿内应力断裂明显，其表面可能经过高温高压处理。365nm长波紫外下，均呈现蓝色、橙红色、黄色和绿色混合的白垩状荧光外观，无磷光现象，而天然紫红色钻石为蓝色荧光或无荧光。宽频诱导发光图像仪GV5000深紫外下均呈现橙红色和蓝色混合荧光，无磷光现象。红外光谱中红外区均显示集合体氮相关的A中心和B中心，归类为IaAB型，且具有H1a辐照退火相关的特征峰，红外光谱近红外区均显示H1b，H1c辐照退火相关的特征峰与H₂中心的特征峰。紫外可见近红外分光光度计均显示明显的NV-中心，H₂中心和806 nm吸收峰，400～460和570 nm宽带处反射率的变化分别与N₃中心和NV0中心相关，明显的NV-中心在天然紫红色钻石中极少发现，H₂中心指示可能经过高温高压处理，可见光范围内对红光和蓝光的吸收较弱，所以呈现为紫红色外观。三维荧光光谱和光致发光光谱均显示出N₃，H₃，H₄，NV0, NV-相关的发光中心，N₃贡献蓝色荧光，H₃和H₄贡献黄绿色荧光，NV0与NV-贡献橙红色荧光。综合分析，三颗样品均为天然成因的钻石，后期经过高温高压，辐照，退火等多重处理，其紫红色主要由N₃中心，NV0中心与NV-中心共同贡献。

Spectroscopic Characteristics and Identification Methods of Color-Treated Purplish Red Diamonds

Based on the analysis of the spectral characteristics of round faceted color-treated purplish-red diamonds from the domestic market,the identification of this kind of diamonds is confirmed.The sample diamonds are purplish-red with different saturation,and the specific gravity of the hydrostatic weighing method is 3.52.Magnification observation shows that partial facets with the weaker luster of DR-2 and DR-3 have ablative areas that are not re-polished,and graphitization is also obvious along with internal stress fracture,both indicating that samples have been treated with high temperature and high pressure.Under the long-wavelength ultraviolet of 365 nm,the chalky fluorescence appearance of blue,orange-red,yellow and green is mixed,and the phosphorescence phenomenon is absent,which is different from the blue fluorescence or no fluorescence phenomenon of nature-colored purplish-red diamonds.Under GV5000,orange-red and blue mixed fluorescence is observed,and the phosphorescence phenomenon is absent.In the mid-infrared spectra,A center and B center,which show aggregation nitrogen correlation,are classified into IaAB type and have characteristic peaks related to H1a radiation annealing,while in the near-infrared spectra,characteristic peaks of H1b,H1c related to irradiation annealing and characteristic peaks of H₂ center are shown.UV-VIS-NIR spectra shows obvious NV-,H₂ and 806 nm absorption peak;400~460 and 570 nm broadband reflectivity changes are associated with N₃ and NV⁰ respectively.Obvious NV-is rarely found in natural purplish-red diamonds and H₂ indicates diamonds may be treated with high temperature and high pressure.Furthermore,the low absorption of red light and blue light results in purplish-red appearance.Three-dimension fluorescence spectra and photoluminescence spectra show that N₃,H₃,H₄,NV⁰ and NV-luminescence centers.N₃ contributes blue fluorescence,H₃ and H₄ contribute yellow-green fluorescence,and NV⁰ and NV-contribute orange-red fluorescence.According to the comprehensive analysis,the three samples are all diamonds of natural origin that have undergone multiple treatments such as high temperature and high pressure,irradiation and annealing,etc.,and the purplish-red color is mainly due to the joint contribution of N₃,NV⁰ and NV-.