Nanostructure-based surface-enhanced infrared absorption (SEIRA) spectroscopy has attracted tremendous interest as an ultrasensitive detection tool that supplies chemical-fingerprint information. The interactions between molecular vibrations and plasmons lead to not only the enhancement of spectral intensity, but also the distortion of spectral Lorentzian lineshapes into asymmetric Fano-type or more complicated lineshapes in the SEIRA spectra; this effect hampers the correct readout of vibrational frequencies and intensities for an accurate interpretation of the measured spectra and quantitative analysis. In this work, we investigate the Fano interference between molecular vibrations and plasmons based on exact electrodynamic simulations and theoretical models. We report that, even if the molecular vibrational energy is equal to the plasmon resonant energy, the molecule–nanostructure distance-dependent dipole–dipole interactions, the plasmon-mediated coherent intermolecular interactions and the decay rates of plasmons have a significant impact on the SEIRA lineshapes. This study paves the way for controllable Fano interference at the nanoscale and more studies on plasmon-dressed molecular electronic or vibrational excited states.

中文翻译：

---

揭示表面增强红外吸收光谱中的分子-等离子体相互作用

基于纳米结构的表面增强红外吸收 (SEIRA) 光谱作为一种提供化学指纹信息的超灵敏检测工具引起了极大的兴趣。分子振动和等离子体之间的相互作用不仅导致光谱强度的增强，而且导致光谱洛伦兹线形在 SEIRA 光谱中扭曲成不对称的 Fano 型或更复杂的线形；这种效应妨碍了正确读出振动频率和强度，从而准确解释测量的光谱和定量分析。在这项工作中，我们基于精确的电动力学模拟和理论模型研究了分子振动和等离子体之间的 Fano 干扰。我们报告说，即使分子振动能量等于等离子体共振能量，分子-纳米结构距离相关的偶极-偶极相互作用、等离子体介导的相干分子间相互作用和等离子体的衰变速率对SEIRA线形也有显着影响。这项研究为纳米尺度的可控 Fano 干涉和更多关于等离子体修饰分子电子或振动激发态的研究铺平了道路。