利用吸收和发光光谱技术分析高温高压天然富氢钻石的鉴定特征

对不同类型褐色钻石进行高温高压处理和结构特性研究是钻石研究中的难点和重点之一。前人对富氢钻石的研究主要集中于其特殊的生长结构以及其形成环境的探讨,而对富氢钻石经高温高压处理后的变化特征鲜有涉及。本文对经高温高压处理前后的富氢钻石的红外光谱、紫外可见吸收光谱以及光致发光光谱等谱学特征进行了对比,研究其鉴定特征。结果表明:高温高压处理前后的富氢钻石的光谱特征具有明显差异,特别是红外光谱,经处理后的钻石中与氮氢有关的吸收峰如3310 cm~(-1)、3232 cm~(-1)、3189 cm~(-1)等明显减弱甚至消失,并出现与孤氮有关的新的2688 cm~(-1)吸收峰;紫外可见光吸收光谱中,经处理的褐色钻石中的无选择性吸收(钻石呈褐色的原因)变为孤氮的典型吸收,即550 nm至短波的吸收以及N_3中心(415 nm)的吸收均明显增强,因此钻石也由原来的褐色变为黄色。钻石经处理前后的光致发光光谱中,与氮原子有关的缺陷类型、峰的强度以及缺陷组合也有变化。本文获得的光谱变化特征,为准确鉴定高温高压处理的黄色富氢钻石提供了依据,也为解释与氢和氮相关的晶格缺陷在高温条件下的变化机理提供了理论基础。

Identification of HPHT-treated Hydrogen-rich Diamonds by Optical Absorption and Photo Luminescence Spectroscopy Techniques

Research on different types of brown diamonds under high temperature and high pressure and their structural characteristics is one of the most difficult and important issues in diamond research. Previous studies on hydrogen-rich diamond mainly focused on its special growth structure and the formation environment, but rarely on the characteristics of hydrogen-rich diamond after high temperature and high pressure treatment. The spectral characteristics of the hydrogen-rich diamonds before and after high temperature and high pressure treatment, including Infrared Spectra, UV-vis Absorption Spectra, and Photoluminescence Spectra were compared and their identification characteristics were studied. Results show that the spectroscopic features are different for the samples before and after the high temperature and high pressure treatment, epecially for infrared spectra. Absorption peaks related to H and N at 3310 cm^-1, 3232 cm^-1, 3189 cm^-1 weakened obviously or even disappeared. Moreover, the absorption peak at 2688 cm^-1 related to isolated nitrogen appeared. In the UV-Vis absorption spectrum, the non-selective absorption in treated brown diamonds became the typical isolated nitrogen absorption, which means that the absorption of 550 nm to shortwave and the absorption of the center of N₃ (415 nm) increased obviously. Therefore, the diamond changed from the original brown to yellow. The photoluminescence spectra before and after treatment of diamonds also vary with the types of nitrogen-related defects, peak intensities, and defect combinations. The spectral characteristics obtained not only provide a basis for the accurate identification of yellow, hydrogen-rich diamonds treated by high temperature and high pressure, but also provide a theoretical basis for explaining the change mechanism of hydrogen-and nitrogen-related lattice defects under high temperature.