Large metallic nanoparticles with sizes comparable to the wavelength of light are expected to support high-order plasmon modes exhibiting resonances in the visible to near infrared spectral range. However, the radiation behavior of high-order plasmon modes, including scattering spectra and radiation patterns, remains unexplored. Here, we report on the first observation and characterization of the high-order plasmon modes excited in large gold nanospheres by using the surface plasmon polaritons generated on the surface of a thin gold film. The polarization-dependent scattering spectra were measured by inserting a polarization analyzer in the collection channel and the physical origins of the scattering peaks observed in the scattering spectra were clearly identified. More interestingly, the radiation of electric quadrupoles and octupoles was resolved in both frequency and spatial domains. In addition, the angular dependences of the radiation intensity for all plasmon modes were extracted by fitting the polarization-dependent scattering spectra with multiple Lorentz line shapes. A significant enhancement of the electric field was found in the gap plasmon modes and it was employed to generate hot-electron intraband luminescence. Our findings pave the way for exploiting the high-order plasmon modes of large metallic nanoparticles in the manipulation of light radiation and light–matter interaction.

中文翻译：

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表面等离激元极化子激发的大金纳米球的高等离激元模式的辐射†

尺寸与光波长可比的大型金属纳米粒子有望支持高阶等离激元模式，这些模式在可见光到近红外光谱范围内均显示出共振。但是，包括散射光谱和辐射图在内的高阶等离子体激元模式的辐射行为仍未得到探索。在这里，我们通过使用在薄金膜表面产生的表面等离激元极化子，对在大型金纳米球中激发的高阶等离激元模式的首次观察和表征进行了报道。通过在收集通道中插入偏振分析仪来测量与偏振有关的散射光谱，并且可以清楚地识别在散射光谱中观察到的散射峰的物理起源。更有趣的是，电四极子和八极子的辐射在频域和空间域均得到了解析。此外，通过将偏振相关的散射光谱与多个洛伦兹线形状拟合，可以提取所有等离激元模式的辐射强度的角度依赖性。在间隙等离子体激元模式中发现电场的显着增强，并用于产生热电子带内发光。我们的发现为在操纵光辐射和光-物质相互作用中利用大型金属纳米粒子的高阶等离激元模式铺平了道路。在间隙等离子体激元模式中发现电场的显着增强，并用于产生热电子带内发光。我们的发现为在操纵光辐射和光-物质相互作用中利用大型金属纳米粒子的高阶等离激元模式铺平了道路。在间隙等离子体激元模式中发现电场的显着增强，并用于产生热电子带内发光。我们的发现为在操纵光辐射和光-物质相互作用中利用大型金属纳米粒子的高阶等离激元模式铺平了道路。