Development of ab-initio simulation methods for molecules in an intense laser field

我们看到阿秒技术的显著进步，它使用超短强激光脉冲来观察和操纵原子和分子中的电子运动。本文采用精确含时薛定谔方程模拟方法，研究了阿秒XUV脉冲作用下激发态He原子的单光子电离。我们发现了出射的内层电子与外层电子碰撞的“knock-up”现象，并发展了一种新的从头算方法来模拟强激光场中的多电子动力学。这种方法，称为时间相关的完全活性空间自洽场（TD-CASSCF）方法，引入了核心和活性轨道子空间的概念，允许紧凑而准确的表示多电子动力学。该方法为强激光场中原子和分子的第一性原理理论研究开辟了一条新的途径。

We see remarkable progress in attosecond technology that uses ultrashort intense laser pulses to observe and manipulate electronic motion in atoms and molecules. Especially, multi-electron and electron correlation effects are attracting increasing interest.We have studied single-photon ionization of an excited He atom by an attosecond XUV pulse, using the exact time-dependent Schrodinger equation simulations. We have discovered "knock-up" phenomena where the outgoing inner electron collides with the outer electron.Further, we have developed a new ab-initio method to simulate multi-electron dynamics in an intense laser field. This method, called the time-dependent complete-active-space self-consistent-field (TD-CASSCF) method, introduces the concept of core and active orbital subspaces, allowing compact yet accurate representation of many-electron dynamics. This method will open a way to the first-principles theoretical study of realistic atoms and molecules in intense laser fields.