In strong field ionization, the pump pulse not only photoionizes the molecule, but also drives efficient population exchanges between its ionic ground and excited states. In this study, we investigate the population dynamics after strong field molecular photoionization, using angular distribution of dissociative fragments. Our results reveal that the first and third order processes of the post-ionization population redistribution mechanism (PPRM) in the ion can be disentangled and classified by its angle-resolved kinetic energy release (KER) spectra. We demonstrate that the imprints of PPRM in the KER spectra can be used to determine the branching ratio of the population exchange pathways of different orders, by exploiting the pump-intensity-dependent variation of the spectra.

中文翻译：

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强场中电离化种群再分布的三阶效应

在强场电离中，泵浦脉冲不仅使分子光电离，而且还驱动其离子基态和激发态之间的有效种群交换。在这项研究中，我们使用解离碎片的角度分布研究了强场分子光电离后的种群动态。我们的结果表明，离子中电离后粒子群再分布机制 (PPRM) 的一阶和三阶过程可以通过其角分辨动能释放 (KER) 光谱进行解开和分类。我们证明，通过利用光谱的泵浦强度依赖性变化，KER 光谱中 PPRM 的印记可用于确定不同顺序的种群交换途径的分支比。