The acetylene-vinylidene system serves as a benchmark for investigations of ultrafast dynamical processes where the coupling of the electronic and nuclear degrees of freedom provides a fertile playground to explore the femto- and sub-femto-second physics with coherent extreme-ultraviolet (EUV) photon sources both on the table-top as well as free-electron lasers. We focus on detailed investigations of this molecular system in the photon energy range 19–40 eV where EUV pulses can probe the dynamics effectively. We employ photoelectron–photoion coincidence (PEPICO) spectroscopy to uncover hitherto unrevealed aspects of this system. In this work, the role of excited states of the C₂H₂⁺ cation, the primary photoion, is specifically addressed. From photoelectron energy spectra and angular distributions, the nature of the dissociation and isomerization channels is discerned. Exploiting the 4π-collection geometry of the velocity map imaging spectrometer, we not only probe pathways where the efficiency of photoionization is inherently high but also perform PEPICO spectroscopy on relatively weak channels.

中文翻译：

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乙炔分子的重合角分辨状态选择光电子能谱：时间分辨动力学的候选系统

乙炔-亚乙烯基系统可作为研究超快动力学过程的基准，其中电子和核自由度的耦合为研究具有相干极紫外（EUV）的飞秒和飞秒级物理学提供了肥沃的游乐场。台式和自由电子激光器上的光子源。我们专注于在19-40 eV的光子能量范围内对该分子系统的详细研究，其中EUV脉冲可以有效地探测动力学。我们使用光电子-光子重合（PEPICO）光谱来揭示该系统迄今尚未揭示的方面。在这项工作中，C ₂ H ₂ ⁺的激发态的作用阳离子，即主要的光子离子，得到了专门解决。从光电子能谱和角度分布，可以看出离解和异构化通道的性质。利用速度图成像光谱仪的4π收集几何结构，我们不仅探测了固有电离效率高的途径，而且还在相对较弱的通道上进行了PEPICO光谱学研究。