A new time-dependent configuration interaction method has been developed for simulating strong field sequential double ionization of molecular systems. Ionization of the neutral is simulated by time-dependent configuration interaction with single excitations (TD-CIS) and an absorbing boundary. At each time step, the ionized part of the wavefunction from the TD-CIS calculation is transferred to a second time-dependent configuration interaction simulation for ionization of the cation to the dication. The second simulation uses a CISD-IP wavefunction that consists of singly ionized configurations and singly excited, singly ionized configurations (TD-CISD-IP). The transfer between the TD-CIS and TD-CISD-IP simulations is accomplished by partitioning the first ionization rate into contributions from individual orbitals or by singular value decomposition of the absorbed wavefunction. Sequential double ionization simulations have been carried out for HBr in five cycle 800 nm linearly polarized pulses and HI (with spin–orbit coupling) in four cycle 800 nm circularly polarized pulses, with intensities chosen so that the population of the neutral was depleted by the mid-pulse. The singular value decomposition of the cation produced by the first ionization is dominated by a single component for the two orientations considered. The population of the cation rises and then falls as it is ionized to the dication. Depending on the pulse shape and field strength, the ionization of the cation to the dication can continue for several half cycles. For HI with circularly polarized light, the rates for both the first and second ionization peak when the electric field is aligned with the p_π orbital.

中文翻译：

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用瞬态构型相互作用模拟的强激光场对分子的顺序双电离

开发了一种新的瞬态构型相互作用方法，用于模拟分子系统的强场序双电离。中性的电离是通过与单激发 (TD-CIS) 和吸收边界的时间相关配置相互作用来模拟的。在每个时间步长，来自 TD-CIS 计算的波函数的电离部分被转移到第二个依赖于时间的构型相互作用模拟，以将阳离子电离为双阳离子。第二个模拟使用由单电离配置和单激发单电离配置 (TD-CISD-IP) 组成的 CISD-IP 波函数。TD-CIS 和 TD-CISD-IP 模拟之间的转换是通过将第一电离率划分为来自各个轨道的贡献或通过吸收波函数的奇异值分解来完成的。已经对 HBr 在五个周期的 800 nm 线性极化脉冲和 HI（具有自旋轨道耦合）在四个周期的 800 nm 圆极化脉冲中进行了连续双电离模拟，强度的选择使得中性粒子的数量被耗尽中脉。对于所考虑的两个方向，第一次电离产生的阳离子的奇异值分解由单个分量支配。阳离子的数量上升然后下降，因为它被电离到双阳离子上。根据脉冲形状和场强，阳离子电离成双阳离子可以持续几个半周期。对于圆偏振光的 HI，当电场与 p 对齐时第一个和第二个电离峰的速率_π轨道。