The most common mid-infrared (MIR) attenuated total reflection (ATR) accessory has a nominal angle of incidence of 45° and does not have a polarizer. A spectrum recorded with such an accessory does not hold enough information for the sophisticated ATR correction of MIR spectra with strong peaks, which are often strongly affected by refractive index changes due to anomalous dispersion. Here we show that a 45° ATR spectrum recorded without a polarizer and the polarization angle for the same ATR Fourier transform infrared spectroscopy system provide enough information to determine the ATR s-polarized spectrum. Further analysis with an improved non-iterative Kramers–Kronig analysis immediately yields the complex refractive index function. The analysis is about two orders of magnitude faster than iterative formalism and runs within seconds on a typical office PC. The effectiveness of our advanced ATR correction formalism is showcased through its application to water, employing diamond, ZnSe, and Ge ATR crystals, along with two distinct ATR accessories. Additionally, the formalism is applied to octadecane spectra. Potential sources of errors such as incidence angle spread, dispersion of the polarization angle, and the influence of reflection at the air/ATR crystal interface are investigated by simulations.

中文翻译：

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在几秒内对 45° 的非偏振入射光进行复杂的衰减全反射校正

最常见的中红外 (MIR) 衰减全反射 (ATR) 附件的标称入射角为 45°，并且没有偏振器。使用此类附件记录的光谱无法保存足够的信息，无法对具有强峰值的 MIR 光谱进行复杂的 ATR 校正，而这些光谱通常会受到反常色散导致的折射率变化的强烈影响。在这里，我们展示了在没有偏振器的情况下记录的 45° ATR 光谱，以及同一 ATR 傅里叶变换红外光谱系统的偏振角提供了足够的信息来确定 ATR s 偏振光谱。使用改进的非迭代 Kramers-Kronig 分析进行进一步分析，立即产生复折射率函数。该分析比迭代形式主义快两个数量级，并且在典型的办公室 PC 上几秒钟内即可运行。我们先进的 ATR 校正形式的有效性通过其在水中的应用（采用金刚石、ZnSe 和 Ge ATR 晶体以及两种不同的 ATR 配件）得以展示。此外，该形式适用于十八烷光谱。通过模拟研究了潜在的误差源，例如入射角扩展、偏振角色散以及空气/ATR 晶体界面处的反射影响。