研究目的
To investigate whether rare earth elements (REEs) have identifiable spectral features in the long-wave infrared (LWIR; 8–12 μm) wavelength range that can be used for their identification.
研究成果
The study concludes that REEs do not induce resolvable diagnostic spectral features in the 8–12 μm wavelength range, which is dominated by the fundamental stretching modes of different mineral groups. Longer wavelengths (14–40 μm) may have potential for direct REE detection, but current spectrometers are limited by atmospheric attenuation beyond 12 μm.
研究不足
The study is limited by the current commercial imaging spectrometers' wavelength range (7.7–12 μm), which does not cover longer wavelengths (14–40 μm) where REEs might have more definitive spectral features. Additionally, spectral mixing and structural distortions could affect the detection of spectral features.
1：Experimental Design and Method Selection:
The study used hyperspectral imaging (HSI) data to investigate the spectroscopy of twelve REE-bearing mineral samples in the LWIR range. The samples were previously characterized using electron probe microanalysis (EPMA), scanning electron microscopy (SEM), and hyperspectral imaging data in the 0.4–2.5 μm range.
2：4–5 μm range.
Sample Selection and Data Sources:
2. Sample Selection and Data Sources: Twelve REE-bearing mineral samples representing fluorocarbonates, phosphates, and silicates were selected. These samples were obtained from private collections and were previously well characterized.
3：List of Experimental Equipment and Materials:
The AisaOWL spectrometer mounted on a LabScanner imaging system by Specim was used for LWIR data acquisition. The Philips XL30 SEM and Cameca SX-100 EPMA were used for sample characterization.
4：Experimental Procedures and Operational Workflow:
Hyperspectral data were acquired in the 7.279–20.797 μm wavelength range, then cropped to 7.797–12.366 μm. Raw data were converted to reflectance using an aluminum standard and a blackbody cavity.
5：279–797 μm wavelength range, then cropped to 797–366 μm. Raw data were converted to reflectance using an aluminum standard and a blackbody cavity.
Data Analysis Methods:
5. Data Analysis Methods: Representative spectra were selected based on signal-to-noise ratios and mineral purity. Spectral features were labeled and compared to reference spectra of rare earth oxides.
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