Strong-field ionization of water. II. Electronic and nuclear dynamics en route to double ionization
Strong-field ionization of water. II. Electronic and nuclear dynamics en route to double ionization
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DOI：
10.1103/physreva.104.023108
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发表时间：
2021-08-23
影响因子：
2.9
通讯作者：
Forbes, Ruaridh
中科院分区：
文献类型：
--
作者：
Cheng, Chuan;Streeter, Zachary L.;Forbes, Ruaridh
我们利用动量分辨符合光谱研究了核运动和强场诱导电子耦合在氘水双电离过程中的作用。通过对少周期和多周期激光脉冲的三体指示解离通道D+/D+/O的研究，观察到脉冲内动力学的有力证据。提取的角分辨和能量分辨双电离产率与经典轨迹模拟的解离动力学进行了比较。与单光子双电离的测量结果相反，即使对持续时间短至10秒的脉冲，也观察到与垂直电离的预期明显偏离。我们概述了许多机制，通过这些机制，强激光场可以在到达分子碎裂发生的最终状态的途中修改核波函数。具体地说，我们考虑了与强场电离率、双电离前单态核的中间运动以及离子中近共振激光诱导的偶极子耦合的坐标依赖性的可能性。这些结果强调了这样一个事实，即对于像D2O这样的小而轻的分子，电离动力学的垂直过渡处理不足以再现在强场重合双电离数据中实验中看到的特征。
We investigate the role of nuclear motion and strong-field-induced electronic couplings during the double ionization of deuterated water using momentum-resolved coincidence spectroscopy. By examining the three-body dicationic dissociation channel, D+/D+/O, for both few- and multicycle laser pulses, strong evidence for intrapulse dynamics is observed. The extracted angle- and energy-resolved double ionization yields are compared to classical trajectory simulations of the dissociation dynamics occurring from different electronic states of the dication. In contrast to measurements of single-photon double ionization, pronounced departure from the expectations for vertical ionization is observed, even for pulses as short as 10 fs in duration. We outline numerous mechanisms by which the strong laser field can modify the nuclear wave function en route to final states of the dication where molecular fragmentation occurs. Specifically, we consider the possibility of a coordinate dependence on the strong-field ionization rate, intermediate nuclear motion in monocation states prior to double ionization, and near-resonant laser-induced dipole couplings in the ion. These results highlight the fact that, for small and light molecules such as D2O, a vertical-transition treatment of the ionization dynamics is not sufficient to reproduce the features seen experimentally in the strong-field coincidence double-ionization data.