Hasegawa Hiroka, Walmsley Tiffany, Matsuda Akitaka, Morishita Toru, Madsen Lars Bojer, Jensen Frank, Tolstikhin Oleg I, Hishikawa Akiyoshi
Graduate School of Science, Nagoya University, Nagoya, Japan.
School of Chemistry, University of Edinburgh, Edinburgh, United Kingdom.
Front Chem. 2022 Apr 14;10:857863. doi: 10.3389/fchem.2022.857863. eCollection 2022.
Dissociative ionization of tetrafluoromethane (CF) in linearly polarized -2 ultrashort intense laser fields (1.4 × 10 W/cm, 800 and 400 nm) has been investigated by three-dimensional momentum ion imaging. The spatial distribution of produced by CF → + F + e exhibited a clear asymmetry with respect to the laser polarization direction. The degree of the asymmetry varies by the relative phase of the and 2 laser fields, showing that 1) the breaking of the four equivalent C-F bonds can be manipulated by the laser pulse shape and 2) the C-F bond directed along the larger amplitude side of the -2 electric fields tends to be broken. Weak-field asymptotic theory (WFAT) shows that the tunneling ionization from the 4 second highest-occupied molecular orbital (HOMO-1) surpasses that from the 1 HOMO. This predicts the enhancement of the tunneling ionization with electric fields pointing from F to C, in the direction opposite to that observed for the asymmetric fragment ejection. Possible mechanisms involved in the asymmetric dissociative ionization, such as post-ionization interactions, are discussed.
通过三维动量离子成像研究了四氟甲烷（CF₄）在线偏振超短强激光场（1.4×10¹⁴W/cm²，800和400nm）中的解离电离。CF₄→CF₃⁺+F+e产生的离子的空间分布相对于激光偏振方向表现出明显的不对称性。不对称程度随基频光和二次谐波激光场的相对相位而变化，表明1）四个等效C-F键的断裂可由激光脉冲形状控制，以及2）沿电场较大振幅侧的C-F键倾向于断裂。弱场渐近理论（WFAT）表明，从第二高占据分子轨道（HOMO-1）的4σ轨道的隧穿电离超过了从最高占据分子轨道（HOMO）的1σ轨道的隧穿电离。这预测了电场从F指向C时隧穿电离的增强，其方向与不对称碎片喷射所观察到的方向相反。讨论了不对称解离电离中涉及的可能机制，如电离后相互作用。
