论文标题
电子和光引起的刺激拉曼光谱纳米级分子映射
Electron and Light Induced Stimulated Raman Spectroscopy for Nanoscale Molecular Mapping
论文作者
论文摘要
我们提出并理论上分析了一种新的振动光谱法，称为电子和光引起的刺激拉曼（ELISR）散射，该散射结合了电子显微镜的高空间分辨率与表面增强拉曼光谱的分子敏感性。使用ELISR，等离激元纳米颗粒的电子梁激发被用作频谱宽带，但在存在衍射限制的泵激光器的情况下，在空间限制的Stokes束。为了表征这种技术，我们开发了一个数值模型并进行全场电磁模拟，以研究两个不同的纳米颗粒几何形状，纳米棒和纳米球，并涂有拉曼活性材料。我们的结果表明，通过双电子和这些纳米颗粒几何形状的光激发可实现明显的（$ 10^6 $ - $ 10^7 $）刺激的拉曼增强。重要的是，该振动光谱对于电子显微镜的空间分辨率仅由纳米颗粒几何形状和等离子体模式体积确定。我们的结果突出了ELISR对同时进行高分辨率电子显微镜的承诺，该电子显微镜与亚分型限制的拉曼光谱，相互分辨率显微镜，相关的光和电子显微镜以及振动电子能量损失的进步。
We propose and theoretically analyze a new vibrational spectroscopy, termed electron- and light-induced stimulated Raman (ELISR) scattering, that combines the high spatial resolution of electron microscopy with the molecular sensitivity of surface-enhanced Raman spectroscopy. With ELISR, electron-beam excitation of plasmonic nanoparticles is utilized as a spectrally-broadband but spatially-confined Stokes beam in the presence of a diffraction-limited pump laser. To characterize this technique, we develop a numerical model and conduct full-field electromagnetic simulations to investigate two distinct nanoparticle geometries, nanorods and nanospheres, coated with a Raman-active material. Our results show the significant ($10^6$-$10^7$) stimulated Raman enhancement that is achieved with dual electron and optical excitation of these nanoparticle geometries. Importantly, the spatial resolution of this vibrational spectroscopy for electron microscopy is solely determined by the nanoparticle geometry and the plasmon mode volume. Our results highlight the promise of ELISR for simultaneous high-resolution electron microscopy with sub-diffraction-limited Raman spectroscopy, complementing advances in superresolution microscopy, correlated light and electron microscopy, and vibrational electron energy loss spectroscopy.
