Structures, kinetics, and chemical reactivities at interfaces and surfaces are key to understanding many of the fundamental scientific problems related to chemical, material, biological, and physical systems. These steady-state and dynamical properties at interfaces and surfaces require even-order techniques with time-resolution and spectral-resolution. Here, we develop fourth-order interface-/surface-specific two-dimensional electronic spectroscopy, including both two-dimensional electronic sum frequency generation (2D-ESFG) spectroscopy and two-dimensional electronic second harmonic generation (2D-ESHG) spectroscopy, for structural and dynamics studies of interfaces and surfaces. The 2D-ESFG and 2D-ESHG techniques were based on a unique laser source of broadband short-wave IR from 1200 nm to 2200 nm from a home-built optical parametric amplifier. With the broadband short-wave IR source, surface spectra cover most of the visible light region from 480 nm to 760 nm. A translating wedge-based identical pulses encoding system (TWINs) was introduced to generate a phase-locked pulse pair for coherent excitation in the 2D-ESFG and 2D-ESHG. As an example, we demonstrated surface dark states and their interactions of the surface states at p-type GaAs (001) surfaces with the 2D-ESFG and 2D-ESHG techniques. These newly developed time-resolved and interface-/surface-specific 2D spectroscopies would bring new information for structure and dynamics at interfaces and surfaces in the fields of the environment, materials, catalysis, and biology.

中文翻译：

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界面/表面特定二维电子光谱的发展

界面和表面的结构、动力学和化学反应性是理解与化学、材料、生物和物理系统相关的许多基本科学问题的关键。界面和表面的这些稳态和动态特性需要具有时间分辨率和光谱分辨率的偶数阶技术。在这里，我们开发了四阶界面/表面特定的二维电子光谱，包括二维电子和频生成 (2D-ESFG) 光谱和二维电子二次谐波生成 (2D-ESHG) 光谱，用于界面和表面的结构和动力学研究。2D-ESFG 和 2D-​​ESHG 技术基于来自自制光学参量放大器的 1200 nm 至 2200 nm 宽带短波红外激光源。使用宽带短波红外光源，表面光谱覆盖了从 480 nm 到 760 nm 的大部分可见光区域。引入了基于平移楔形的相同脉冲编码系统 (TWINs) 来生成锁相脉冲对，用于 2D-ESFG 和 2D-​​ESHG 中的相干激励。作为一个例子，我们展示了表面暗态及其表面态的相互作用p型 GaAs (001) 表面使用 2D-ESFG 和 2D-​​ESHG 技术。这些新开发的时间分辨和界面/表面特异性 2D 光谱将为环境、材料、催化和生物学领域的界面和表面的结构和动力学带来新信息。