Resolving Multiphoton Processes with High-Order Anisotropy Ultrafast X-ray Scattering

Perspective: Ultrafast Imaging of Molecular Dynamics Using Ultrafast Low-Frequency Lasers, X-ray Free Electron Laser and Electron Pulses

The requirement of high space-time resolution and brightness is a great challenge for imaging atomic motion and making molecular movies. Important breakthroughs in ultrabright tabletop laser, x-ray and electron sources have enabled the direct imaging of evolving molecular structures in chemical processes. And recent experimental advances in preparing ultrafast laser and electron pulses equipped molecular imaging with femtosecond time resolution. This Perspectives present an overview of versatile imaging methods of molecular dynamics. High-order harmonic generation imaging and photoelectron dif…

Nonlinearity in the sequential absorption of multiple photons

I classify multiphoton absorption into separable, linked, and simultaneous processes. The first and second types can be distinguished when the rate-equation approximation is valid whereas the third type refers to the case when the full description of multiphoton absorption is essential. For this purpose, rate equations are solved analytically without decay processes which shows that even if many photons are absorbed the interaction with the light field is linear and one has the case of separable multiphoton absorption. Next a short-pulse approximation is investigated in which I first solve the…

强X射线场中CF$_4$分子的透射光谱研究

Transmission spectroscopy of CF$_4$ molecules in intense x-ray fields

本文利用欧洲XFEL强X射线脉冲结合透射光谱技术，研究了CF$_4$分子在多光子吸收下的超快碎裂动力学，实现了对瞬态氟原子和离子的脉冲内观测，并通过等吸光点揭示了分子到带电碎片的转变。

Real-Space Inversion and Super-Resolution of Ultrafast Scattering

Ultrafast scattering using X-rays or electrons is an emerging method to obtain structure dynamics at the atomic length and time scales. However, directly resolving in real-space atomic motions is inherently limited by the finite detector range and the probe energy. As a result, the time-resolved signal interpretation is mostly done in reciprocal space and relies on modeling and simulations of specific structures and processes. Here, we introduce a model-free approach to directly resolve scattering signals in real space, surpassing the diffraction limit, using scattering kernels and signal prio…

利用孤立阿秒脉冲时间分辨光电子的诞生

Time-resolving the birth of photoelectrons in strong-filed ionization with an isolated attosecond pulse

本文提出利用孤立阿秒脉冲通过相干干涉技术时间分辨光电子动态，揭示强场离子化中电子能量与诞生时间的关系。