Department of Physics and Astronomy , University of California , Irvine , California 92697-4575 , United States.
Department of Chemistry , University of California , Irvine , California 92697-2025 , United States.
Nano Lett. 2018 May 9;18(5):3076-3080. doi: 10.1021/acs.nanolett.8b00613. Epub 2018 Apr 18.
The coupling between localized plasmon and molecular orbital in the light emission from a metallic nanocavity has been directly detected and imaged with sub-0.1 nm resolution. The light emission intensity was enhanced when the energy difference between the tunneling electrons and the lowest unoccupied molecular orbital (LUMO) of an azulene molecule matches the energy of a plasmon mode of the nanocavity defined by the Ag-tip and Ag (110) substrate of a scanning tunneling microscope (STM). The spatially resolved image of the light emission intensity matches the spatial distribution of the LUMO obtained by scanning tunneling spectroscopy (STS) and density functional theory (DFT) calculations. Our results highlight the near-field coupling of a molecular orbital to the radiative decay of a plasmonic excitation in a confined nanoscale junction.
金属纳米腔中局域等离子体和分子轨道在光发射中的耦合已被直接探测和成像，分辨率达到亚 0.1nm。当隧道电子和薁分子的最低未占据分子轨道（LUMO）之间的能量差与由 Ag 尖端和扫描隧道显微镜（STM）的 Ag（110）衬底定义的纳米腔的等离子体模式的能量匹配时，光发射强度增强。光发射强度的空间分辨图像与通过扫描隧道光谱（STS）和密度泛函理论（DFT）计算获得的 LUMO 的空间分布相匹配。我们的结果突出了分子轨道与受限纳米结中等离子体激发的辐射衰减的近场耦合。
