We recorded the Raman spectrum of a single azobenzene thiol molecule upon picking it up from an atomically flat gold surface, using an electrochemically etched silver tip, in an ultrahigh vacuum cryogenic scanning tunneling microscope. While suppressed at the junction, the stationary spectrum appeared once the molecule was transferred to the tip, with line intensities that increased by a factor of ∼5 as the tip was retracted from 1 nm to 161 nm. The effect, and the enhanced tensorial Raman spectrum was reproduced using an explicit treatment of the electromagnetic fields to identify a cis-azobenzene thiol molecule, adsorbed on a nanometric asperity removed from the tip apex, lying in the plane normal to the tip z-axis, with enhanced incident and radiative local fields polarized in the same plane. Tips decorated with asperities break the rules and give unique insights on Raman driven by cavity modes of a plasmonic junction.

中文翻译：

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EXPRESS：电化学蚀刻银尖端上单个分子的拉曼光谱

我们在超高真空低温扫描隧道显微镜中使用电化学蚀刻的银尖端从原子级平坦的金表面拾取单个偶氮苯硫醇分子时记录了它的拉曼光谱。虽然在连接处受到抑制，但一旦分子转移到尖端，就会出现固定光谱，随着尖端从 1 nm 缩回至 161 nm，线强度增加了约 5 倍。该效果和增强的张量拉曼光谱是使用电磁场的显式处理再现的，以识别顺式偶氮苯硫醇分子，吸附在从尖端移除的纳米凹凸上，位于垂直于尖端 z 轴的平面上，增强的入射和辐射局部场在同一平面上极化。