Cheng Shuying, Rajarathnam D, Meiling Tan, Garland Marc
Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore 117576.
Appl Spectrosc. 2006 May;60(5):521-8. doi: 10.1366/000370206777412176.
Thermal emission spectral data sets were collected for a thin solid film (parafilm) and a thin liquid film (isopropanol) on the interval of 298-348 K. The measurements were performed using a conventional Fourier transform infrared (FT-IR) spectrometer with external optical bench and in-house-designed emission cell. Both DTGS and MCT detectors were used. The data sets were analyzed with band-target entropy minimization (BTEM), which is a pure component spectral reconstruction program. Pure component emissivities of the parafilm, isopropanol, and thermal background were all recovered without any a priori information. Furthermore, the emissivities were obtained with increased signal-to-noise ratios, and the signals due to absorbance of thermal radiation by gas-phase moisture and CO2 were significantly reduced. As expected, the MCT results displayed better signal-to-noise ratios than the DTGS results, but the latter results were still rather impressive given the low temperatures used in this study. Comparison is made with spectral reconstruction using the orthogonal projection approach-alternating least squares (OPA-ALS) technique. This contribution introduces the primary equation for emission spectral reconstruction using BTEM and discusses some of the unusual characteristics of thermal emission and their impact on the analysis.
在298 - 348 K的温度区间内，收集了薄固体膜（石蜡膜）和薄液体膜（异丙醇）的热发射光谱数据集。测量使用了配备外部光学平台和自行设计的发射池的传统傅里叶变换红外（FT - IR）光谱仪。同时使用了DTGS和MCT探测器。数据集采用带目标熵最小化（BTEM）方法进行分析，BTEM是一种纯组分光谱重建程序。在没有任何先验信息的情况下，成功恢复了石蜡膜、异丙醇和热背景的纯组分发射率。此外，获得的发射率具有更高的信噪比，并且气相水分和二氧化碳对热辐射吸收产生的信号显著降低。正如预期的那样，MCT探测器的结果显示出比DTGS探测器更好的信噪比，但考虑到本研究中使用的低温，DTGS探测器的结果仍然相当可观。文中还与使用正交投影方法 - 交替最小二乘法（OPA - ALS）技术进行光谱重建的结果进行了比较。本论文介绍了使用BTEM进行发射光谱重建的基本方程，并讨论了热发射的一些特殊特性及其对分析的影响。
