稀土反射波谱特征及高光谱提取研究进展

稀土是一种重要的战略资源，由于稀土资源的稀缺，近年来对其反射波谱特征与高光谱信息提取的研究较为薄弱。笔者首先从稀土电子层构型和能级跃迁的层面阐述了其光谱机理。稀土由于其特殊的电子构型，它们的4f电子的f-f组态之内容易跃迁，在可见光-近红外有其特有的波谱吸收特征。其次结合自己开展的一些工作，系统总结了15种稀土单元素、稀土矿物(含稀土的氟碳酸盐、磷酸盐、硅酸盐矿物)、稀土溶液的反射波谱特征，可见15种稀土单元素的反射特征差异较大，稀土矿物及溶液的波谱特征是化学组成中优势稀土元素的体现，吸收强弱随着稀土浓度的降低逐渐减弱甚至消失。由于稀土信息提取对高光谱传感器要求较为苛刻，目前的研究主要集中于近距离高光谱传感器探测，航空及航天高光谱遥感探测存在一定困难，根据单元素的波谱吸收特征，近距离高光谱传感器目前可成功提取Nd，Er，Dy，Ho，Sm和Tm等的分布信息；最后文章展望了稀土反射波谱及高光谱稀土找矿研究的难点和重点，旨在为今后研究提供新的思路。

Reflectance Spectroscopy and Hyperspectral Detection of Rare Earth Element

Today rare earth elements (REE) are of great interest to global economy, and become more and more important in modern technology. However, little research of reflectance spectroscopy and hyperspectral detection of REE has been conducted particularly due to the scarcity of its distribution. In this paper, electronic configuration and energy transition mechanism of REE were explained in the initial stage, for the partial filling of the 4f electron shell combined with numerous 4f-4f intraconfigurational electronic transitions made spectral features of REE unique in visible and infrared wavelength. Then combined with our study, spectral characteristics of fifteen rare earth elements, REE-bearing minerals (REE fluorocarbonates, REE phosphates, REE silicates), REE-bearing solutions were analyzed. The study indicated that spectra of fifteen rare earth elements were different from each other, and the typical distribution of REE (light REE versus heavy REE) in minerals and solutions directly affected their spectral signatures. The spectra of REE-bearing solutions were the combination of spectra of water and REE, and the intensity of absorption features became weaker with the decrease of REE concentration. In addition, hyperspectral REE detection in space borne was hindered by the suitable data source. Some researchers used an in situ instrument (HYSpex sensor) conducting REE mapping, which indicated that hyperspectral mapping of REE was feasible and efficient for Nd, Er, Dy, Ho, Sm, Tm analysis. Hyperspectral imaging spectroscopy of drill core was carried out using sisuROCK instrumentation, and Nd was extracted using its special spectral absorption bands. Finally, future study of REE reflectance spectroscopy and hyperspectral detection was pointed out, and this paper gives a good enlightenment for future exploration of REE using hyperspectral remote sensing.