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二维电子光谱（2DES）是一种超快激光光谱技术，可以探测样品的电子、能量和空间分布。它类似于核磁共振技术，能以高空间分辨率确定复杂的分子结构，是一种能使结构生物学发生革命性变化的光谱技术。2DES是 "终极 "时间分辨非线性光学实验设备，因为它能提供有关系统三阶非线性响应的最大信息量，而且任何其他三阶非线性光谱（如泵浦探针）都包含在二维光谱中。在具有多个相互作用成分的系统中，二维非线性光谱可充分发挥其威力。2DES可提供二维光谱，展现激发与发射频率之间的相关性，同时具有很高的光谱和时间分辨率。2DES可以剖析拥塞的光谱，揭示跃迁之间的分子联系，从而为阐明样品的整体功能提供了一种方法。

Two-dimensional electron spectroscopy (2DES) is an ultrafast laser spectroscopy technique that can detect electrons, energy and spatial distribution of samples. It is similar to nuclear magnetic resonance technology and can determine complex molecular structures with high spatial resolution. It is a spectroscopic technology that can revolutionize structural biology. 2DES is the "ultimate" time-resolved nonlinear optics experimental device because it provides the greatest amount of information about the third-order nonlinear response of the system than any other third-order nonlinear spectroscopy (e.g., pump-probe) are included in the two-dimensional spectrum. In systems with multiple interacting components, 2D nonlinear spectroscopy can realize its full power. 2DES provides two-dimensional spectra showing the correlation between excitation and emission frequencies with high spectral and temporal resolution. 2DES can dissect congested spectra and reveal the molecular connections between transitions, providing a way to elucidate the overall functionality of a sample.

原子运动及相应的结构改变是自然界中化学反应、生命过程等现象的本质。因此，在原子层面实时间、实空间观测物质非平衡态的原子运动和结构演化过程，能深刻地解释这些现象的本质，将物质的微观动力学过程和其物理化学等特性联系起来，为科学突破创造了巨大的机遇。原子层面的动态过程的特征时间在皮秒、飞秒、甚至阿秒量级，目前只有泵浦-探测技术可以实现该量级的时间分辨率。超快电子衍射使用电子作为泵浦-探测技术中的探针，具有高弹性散射截面、低能量沉积、造价及维护成本低等优势，在近十余年间获得快速发展。

Atomic motion and corresponding structural changes are the essence of chemical reactions, life processes and other phenomena in nature. Therefore, observing the atomic motion and structural evolution process of non-equilibrium states of matter at the atomic level in real time and real space can profoundly explain the nature of these phenomena, connect the microscopic dynamic process of matter with its physical and chemical properties, and provide scientific Breakthroughs create huge opportunities. The characteristic time of dynamic processes at the atomic level is on the order of picoseconds, femtoseconds, or even attoseconds. Currently, only pump-detection technology can achieve time resolution of this level. Ultrafast electron diffraction uses electrons as probes in pump-detection technology. It has the advantages of high elastic scattering cross section, low energy deposition, low construction and maintenance costs, and has achieved rapid development in the past ten years.

人类在探索自然界中各种物理规律的过程中对于瞬态时间尺度的物理现象的研究从未停止。利用更高的时间分辨率来探索更短时间内发生的物理过程一直是物理、生物乃至化学等研宄领域的重要方向。物质中分子的转动与振动过程分别发生在皮秒和飞秒量级， 测量这些运动过程需要飞秒量级的时间分辨， 虽然商业钛宝石激光放大系统己经能够实现25 fs 左右的脉冲输出， 但这样的脉冲宽度还未到达少周期级别，用于研究分子和原子内部阿秒量级的电子运动还远远不够。高次谐波产生是一种极端的非线性效应，强场激光聚焦到气体介质上的时候，会发生非线性效应，可以得到上百阶的高能谐波光子。作为一种相干的宽谱高能光源，它可以用来产生阿秒脉冲。把飞秒激光聚焦到气体/图固体源中，就可以产生高能光子。产生高次谐波需要的场强需要达到 100 TW/cm2 量级，因此需要一台脉冲能量为毫焦级、脉冲长度在少周期量级的激光器来产生。

In the process of exploring various physical laws in nature, human beings have never stopped studying physical phenomena on transient time scales. Using higher time resolution to explore physical processes occurring in shorter periods of time has always been an important direction in research fields such as physics, biology and even chemistry. The rotation and vibration processes of molecules in matter occur at the picosecond and femtosecond levels respectively. Measuring these motion processes requires femtosecond time resolution. Although commercial titanium sapphire laser amplification systems can already achieve pulse output of about 25 fs, However, such pulse width has not yet reached the low-period level, and it is far from sufficient for studying the attosecond-level electron motion inside molecules and atoms. The generation of high-order harmonics is an extreme nonlinear effect. When a strong-field laser is focused on a gas medium, a nonlinear effect will occur, and hundreds of high-energy harmonic photons can be obtained. As a coherent broad-spectrum high-energy light source, it can be used to generate attosecond pulses. High-energy photons can be generated by focusing a femtosecond laser into a gas/solid source. The field strength required to generate high-order harmonics needs to be on the order of 100 TW/cm2, so a laser with a pulse energy of millijoules and a pulse length of a few cycles is required to generate it.