隧穿电离（TI）是高次谐波产生、强场电离等众多重要超快过程的基础。在现有的隧穿电离理论中，多电子弱场渐近理论（ME-WFAT）在设计上能够精准处理隧穿电离过程中的多电子效应。早期版本的ME-WFAT依赖于对轨道渐近尾部的精准表征，这一特性阻碍了其在基于高斯基组的量子化学程序中的实现。在本研究中，我们以积分表示形式重新构建了ME-WFAT，大幅降低了轨道渐近尾部质量对计算的影响，从而极大地推动了其在标准量子化学软件包中的落地应用。因此，本文提出的积分重构方法在应用于任意几何构型的分子时，鲁棒性显著提升。我们开展了多项案例研究，其中包括CO分子——此前部分理论的计算结果与实验结果存在分歧。本研究发现，正如实验所表明的，当电场方向由C指向O时，ME-WFAT计算得到的电离概率最大。ME-WFAT的一大优势在于它可适配多种多电子方法，无论是密度泛函类方法[Phys. Rev. A 106, 052211 (2022)]还是多组态类方法，这反过来又为具有强多参考特征的体系的隧穿电离计算提供了便利。
英文摘要：
Tunnel ionization (TI) underlies many important ultrafast processes, such as high-harmonic generation and strong-field ionization. Among the existing theories for TI, many-electron weak-field asymptotic theory (ME-WFAT) is by design capable of accurately treating many-electron effects in TI. An earlier version of ME-WFAT relied on an accurate representation of the asymptotic tail of the orbitals, which hindered its implementation in Gaussian-basis-set-based quantum chemistry programs. In this work, we reformulate ME-WFAT in the integral representation, which makes the quality of the asymptotic tail much less critical, hence greatly facilitating its implementation in standard quantum chemistry packages. The integral reformulation introduced here is therefore much more robust when applied to molecules with arbitrary geometry. We present several case studies, among which is the CO molecule where some earlier theories disagree with experiments. Here, we find that ME-WFAT produces the largest ionization probability when the field points from C to O, as experiments suggest. An attractive feature of ME-WFAT is that it can be used with various types of multielectron methods whether of density functional [Phys. Rev. A 106, 052211 (2022)] or multiconfiguration types, this in turn facilitates tunnel ionization calculation in systems exhibiting a strong multireference character.
Fine- and hyperfine-structure effects in molecular photoionization: II. Resonance-enhanced multiphoton ionization and hyperfine-selective generation of molecular cations
Influence of molecular symmetry on strong-field ionization: Studies on ethylene, benzene, fluorobenzene, and chlorofluorobenzene
利用分子强场近似，我们考虑了分子对称性对强线偏振激光脉冲电离分子的影响。电子角分布和总电离产率计算作为分子和激光偏振之间的相对取向的函数。我们的研究集中在乙烯（C $_2$ H $_4$）、苯（C $_6$ H $_6$）、氟苯（C $_6$ H $_5$ F）和邻氯氟苯（1，2 C $_6$ H $_4$ ClF），这些分子代表四种不同的点群。实验结果进行了比较，当可用时，并与适当扩展到非线性多原子分子的分子隧穿理论。我们的研究表明，电离产率的取向依赖性主要是由节点表面结构的分子轨道。
