基于太赫兹时域光谱技术的白色软玉产地鉴定研究

Origin identification of white nephrite based on terahertz time-domain spectroscopy

不同产地的白色软玉组成矿物成分和结构构造十分相近,但价值差异很大。太赫兹(terahertz,THz)时域光谱技术可以提供物质的化学组成、结构及构像等信息,光谱指纹特征信息可用于物质鉴别。利用透射式太赫兹时域光谱技术分别对新疆、韩国、青海和俄罗斯这4个产地的白色软玉进行了测试,将得到的时域光谱进行快速傅里叶变换(fast Fourier transform,FFT)和计算后使用Savitzky-Golay(S-G)平滑处理进行降噪,得到4个产地白色软玉的0.2~2.5 THz频域内折射率和吸收系数。研究表明,4个产地白色软玉THz光谱折射率存在数值差异;不同产地太赫兹特征吸收峰的存在形式不同,新疆、青海的白色软玉在2.0 THz波段有1个突出的小型特征吸收峰,而韩国和俄罗斯的白色软玉在1.5~2.0 THz波段有1个宽大的吸收包络。这些结果为进一步开发基于太赫兹时域光谱技术的白色软玉产地识别方法提供了基础数据。

White nephrites of different origins are quite similar to each other in main mineral composition and structure, but their values vary greatly. Terahertz time-domain spectroscopy( THz-TDS) technology can not only provide information on chemical composition of substances but also provide spectral fingerprint information related to structure and conformation for substances identification. In this study, THz-TDS was used to test the white nephrite from four producing areas, i. e., Xinjiang, South Korea, Qinghai and Russia, whose refractive indexes and absorption coefficients in the frequency domain of 0. 2 ~ 2. 5 THz were obtained after fast Fourier transform( FFT) and calculation followed by Savitzky-Golay( S-G) smoothing. The results showed that the refractive indexes of the white nephrites from Xinjiang, South Korea, Qinghai and Russian were different. There was a small characteristic absorption at about 2. 0 THz existing in the terahertz characteristics absorption spectra of white nephrites from Xinjiang andQinghai, while a broad absorption envelope in 1. 5 ~ 2. 0 THz band was detected for the white nephrites from Korea and Russia. These results provide basic data for further development of the origin identification method of white nephrites based on terahertz time domain spectroscopy.