AI 中文总结
该研究扩展SFHK传播子方法用于分子HHG计算，结合强场近似，结果精度接近精确数值解，且计算效率高、可并行化。
AI 中文摘要
我们扩展了近期开发的半经典强场Herman-Kluk（SFHK）传播子方法，以计算由少周期强激光场驱动的双原子分子中的高次谐波产生（HHG）。以H₂和N₂为例，我们表明，基于Herman-Kluk传播子与强场近似结合的该方法，能够为HHG产额和相位提供非常准确的结果，与含时薛定谔方程的精确数值解几乎完全一致。为与实验测量对比，必须对分子取向进行平均。此处我们展示了SFHK的一个显著且强大的优势：其用于取向分布积分的蒙特卡洛采样，可与隧穿出射后电子波包初始动量分布的积分高效结合。因此，用于取向平均HHG谱的轨迹总数，与单一固定取向的情况相比不会大幅增加。与原子靶类似，SFHK中的主要计算任务是求解活性电子在电子-靶离子势与电子-激光相互作用组合下的经典哈密顿方程。每个电子波包在连续态中的中心运动由相干态表征，受独立经典轨迹支配，因此计算可高效并行化。
英文摘要
We extend our recently developed semiclassical strong-field Herman-Kluk (SFHK) propagator method to calculate high-order harmonic generation (HHG) in diatomic molecules driven by few-cycle intense laser fields. On the example of applications to H2 and N2, we show that our method, based on a combination of the Herman-Kluk propagator and the strong-field approximation, can provide very accurate results for both HHG yield and phase, nearly identical to those from the exact numerical solutions of the time-dependent Schrodinger equation. To compare with experimental measurements, averaging over molecular orientations must be performed. Here we demonstrate a distinct and powerful advantage of the SFHK, as its Monte Carlo sampling for the integration over the alignment distribution can be efficiently combined with the integration over the initial momentum distributions of electron wave-packet right after the tunnel exit. Therefore, the total number of trajectories used for the alignment-averaged HHG spectrum does not increase much compared to that for a single fixed alignment. Similar to atomic targets, the main computational task in the SFHK is to solve the classical Hamiltonian equations for the active electron in the combined electron-target ion potential and electron-laser interaction. The motion of the center of each electron wave packet in the continuum, represented by a coherent state, is governed by an independent classical trajectory so that the computation can be parallelized very efficiently.
Comments12 pages, 9 figures
