Measured average momentum (<em>P</em>_av), average kinetic energy (KE_av), and the corresponding abundances (1000 eV photon energy)

<b>Table 1.</b> Measured average momentum (<em>P</em>_av), average kinetic energy (KE_av), and the corresponding abundances (1000 eV photon energy). <strong>Abstract</strong> We investigate the multiphoton ionization and the subsequent fragmentation of SF₆ molecules with intense x-ray-free electron laser pulses at different photon energies. We observe highly charged molecular and atomic ions which were absent in previous experiments with conventional x-ray sources. The observation of fully stripped fluorine ions suggests sequential multiphoton ionization processes with intermediate 1s electron excitation. We measure the average momentum and kinetic energy of each fragment, the comparison of which implies many-body fragmentation pathways of the molecular ions. The observed non-monotonic dependence of the kinetic energy on the charge states of fluorine indicates the multiphoton ionization of 'isolated' atomic neutral fluorine or fluorine ions resultant from bond cleavages and also implies the fragmentation of highly charged molecular ions that are produced at a later time during a single pulse.**表1.** 实测平均动量（Pₐᵥ）、平均动能（KEₐᵥ）及对应丰度（光子能量为1000 eV）。 **摘要** 本研究针对不同光子能量下的强X射线自由电子激光（X-ray-free electron laser）脉冲与六氟化硫（SF₆）分子的多光子电离及后续碎裂过程展开探究。实验中观测到了常规X射线源既往实验未曾发现的高荷电分子离子与原子离子。全剥离氟离子的观测结果表明，反应存在伴随中间1s电子激发的顺序多光子电离过程。我们对每一个碎裂产物的平均动量与动能进行了测量，通过二者的对比分析可推导出分子离子的多体碎裂路径。观测到的动能随氟离子荷电态变化的非单调依赖关系，既指向了化学键断裂产生的‘孤立’中性氟原子或氟离子的多光子电离过程，也揭示了单脉冲后期生成的高荷电分子离子的碎裂机制。