研究目的
Investigating the technique and experimental laboratory setup for recording the specular and diffuse reflectance spectra of the infrared radiation of substances in solid and liquid aggregate states on various surfaces using a quantum cascade laser.
研究成果
The experimental setup and the method for analyzing substances on an ideal non-scattering substrate allow detecting and identifying a wide range of substances in various aggregate states with a sufficiently high probability. The use of the Kramers–Kronig transform allows increasing the reliability of the detection of substances by the reflected radiation.
研究不足
The diffuse reflectance spectra have a weak selectivity and depend on the pattern of the recording of reflected radiation. Specularly reflected radiation can introduce phase distortions into the spectrum of the substance.
1：Experimental Design and Method Selection:
The experimental setup was developed to register scattered infrared radiation from the samples of chemical compounds in the solid and liquid aggregate states on various underlying surfaces using a QCL tunable in the wavelength range of
2：3–8 μ m and a MCT photodetector. Sample Selection and Data Sources:
The test substances were placed on the substrate, and the scattered radiation spectrum was recorded.
3：List of Experimental Equipment and Materials:
The elements of the LaserTune system (Block Engineering, USA) were used as a QCL and photodetector.
4：Experimental Procedures and Operational Workflow:
The photodetector and the collecting lens were aligned to collect maximum scattered radiation. The photodetector was positioned at an angle of 30°–45° to the normal to the substrate to minimize specularly reflected radiation.
5：Data Analysis Methods:
The normalized diffuse reflectance spectrum R(ν) was calculated as R(ν) = I(ν)/I0(ν). The Kramers–Kronig integral transform was used to calculate the absorption spectra from the scattering spectra.
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