Xie Wenhai, Yan Jiaqing, Li Min, Cao Chuanpeng, Guo Keyu, Zhou Yueming, Lu Peixiang
Wuhan National Laboratory for Optoelectronics and School of Physics, Huazhong University of Science and Technology, Wuhan 430074, China.
Hubei Key Laboratory of Optical Information and Pattern Recognition, Wuhan Institute of Technology, Wuhan 430205, China.
Phys Rev Lett. 2021 Dec 24;127(26):263202. doi: 10.1103/PhysRevLett.127.263202.
Laser-induced tunneling ionization is one of the fundamental light-matter interaction processes. An accurate description of the tunnel-ionized electron wave packet is central to understanding and controlling subsequent electron dynamics. Because of the anisotropic molecular structure, tunneling ionization of molecules involves considerable challenges in accurately describing the tunneling electron wave packet. Up to now, some basic properties of the tunneling electron from molecules still remain unexplored. Here, we demonstrate that the tunneling electron from a molecule is not always emitted from the geometric center of the molecule along the tunnel direction. Rather, the photoemission position depends on the molecular orientation. Using a photoelectron holographic technique, we determine the photoemission position for a nitrogen molecule relative to the molecular geometric center to be 95±21 pm when the molecular axis is oriented along the tunnel direction. Our Letter poses, and answers experimentally, a fundamental question as to where the molecular photoionization actually begins, which has significant implications for time-resolved probing of valence electron dynamics in molecules.
激光诱导隧穿电离是基本的光与物质相互作用过程之一。准确描述隧穿电离电子波包是理解和控制后续电子动力学的核心。由于分子结构的各向异性，分子的隧穿电离在精确描述隧穿电子波包方面面临诸多挑战。到目前为止，分子隧穿电子的一些基本性质仍未被探索。在此，我们证明分子的隧穿电子并非总是沿隧穿方向从分子的几何中心发射。相反，光发射位置取决于分子取向。利用光电子全息技术，当分子轴沿隧穿方向取向时，我们确定氮分子相对于分子几何中心的光发射位置为95±21皮米。我们的论文提出并通过实验回答了一个关于分子光电离实际从何处开始的基本问题，这对分子价电子动力学的时间分辨探测具有重要意义。
