Department of Chemistry, James Franck Institute, and Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, United States.
J Phys Chem Lett. 2021 Dec 16;12(49):11843-11849. doi: 10.1021/acs.jpclett.1c03432. Epub 2021 Dec 6.
Reflection mode two-dimensional infrared spectroscopy (R-2DIR) has recently emerged as a tool that expands the utility of ultrafast IR spectroscopy toward a broader class of materials. The impact of experimental configurations on the potential distortions of the transient reflectance (TR) spectra has not been fully explored, particularly in the vicinity of the critical angle θ and through the crossover from total internal reflection to partial reflection. Here we study the impact on the spectral lineshape of a dilute bulk solution as θ is varied across the incident angle by tuning the refractive index of the solvent. We demonstrate the significance of several distortions, including the appearance of phase twisted lineshapes and apparent changes in the spectral inhomogeneity, and show how these distortions impact the interpretation of the TR and R-2DIR spectroscopies.
反射模式二维红外光谱学（R-2DIR）最近成为一种工具，它将超快红外光谱学的应用扩展到更广泛的材料类别。实验配置对瞬态反射（TR）光谱潜在失真的影响尚未得到充分探索，特别是在临界角θ附近以及从全内反射到部分反射的转变过程中。在这里，我们通过调节溶剂的折射率来研究随着入射角θ的变化，对稀散装溶液光谱线形状的影响。我们演示了几种失真的重要性，包括相位扭曲线形状的出现和光谱不均匀性的表观变化，并展示了这些失真如何影响 TR 和 R-2DIR 光谱学的解释。
