Enhanced ionisation of polyatomic molecules in intense laser pulses is due to energy upshift and field coupling of multiple orbitals
Enhanced ionisation of polyatomic molecules in intense laser pulses is due to energy upshift and field coupling of multiple orbitals
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DOI：
10.1088/1361-6455/aa7098
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发表时间：
2017-06-28
影响因子：
1.6
通讯作者：
Kitzler, Markus
中科院分区：
文献类型：
--
作者：
Erattupuzha, Sonia;Covington, Cody L.;Kitzler, Markus
我们提出的结果相结合的实验和数值研究的强场电离乙炔进行的目的是确定背后的机制，以前报道的令人惊讶的大多电子电离概率的多原子分子。使用符合动量成像技术和含时密度泛函模拟，我们表明，报告的有效电离是由于一个显着的几何诱导的能量上移的最相关的价轨道的C-H距离拉伸超过约两倍的平衡距离，并在多个分子轨道之间的耦合伴随着这种拉伸运动的强烈增加的联合行动。所确定的增强电离机制，我们称之为EIC-MOUSE，仅对接近平行于激光偏振方向排列的分子有效，并且由于电离开始期间C-H拉伸运动的抑制而对垂直排列的分子被抑制。
We present the results of a combined experimental and numerical study on strong-field ionisation of acetylene performed with the aim of identifying the mechanism behind the previously reported surprisingly large multi-electron ionisation probabilities of polyatomic molecules. Using coincidence momentum imaging techniques and time-dependent density functional simulations, we show that the reported efficient ionisation is due to the combined action of a significant geometrically induced energy upshift of the most relevant valence orbitals as the C-H distance stretches beyond about two times the equilibrium distance, and a strong increase in the coupling between multiple molecular orbitals concomitant with this stretch motion. The identified enhanced ionisation mechanism, which we refer to as EIC-MOUSE, is only effective for molecules aligned close to parallel to the laser polarisation direction, and is inhibited for perpendicularly aligned molecules because of a suppression of the C-H stretch motion during the onset of ionisation.