Following the Birth of a Nanoplasma Produced by an Ultrashort Hard-X-Ray Laser in Xenon Clusters
Following the Birth of a Nanoplasma Produced by an Ultrashort Hard-X-Ray Laser in Xenon Clusters
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DOI：
10.1103/physrevx.8.031034
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发表时间：
2018-08-02
影响因子：
12.5
通讯作者：
Ueda, Kiyoshi
中科院分区：
文献类型：
--
作者：
Kumagai, Yoshiaki;Fukuzawa, Hironobu;Ueda, Kiyoshi
X 射线自由电子激光器 (XFEL) 提供了一种新的 X 射线强度体系，彻底改变了超快结构测定，并为非线性 X 射线光学新领域奠定了基础。尽管早期的研究揭示了 XFEL 脉冲与任何纳米级物质相互作用时纳米等离子体的形成，但形成过程本身从未被解密，其时间尺度也是未知的。在这里，我们展示了时间分辨离子产率测量与近红外激光探针相结合，揭示了令人惊讶的超快布居（类似于 12 fs），随后在 XFEL 诱导的纳米等离子体形成过程中产生的原子碎片的高度激发态的缓慢减少（类似于 250 fs）。俄歇电子的非弹性散射和原子间库仑衰变被认为分别是这些激发态的填充和减少的机制。观察到的响应发生在典型的 X 射线脉冲持续时间内，并影响 X 射线散射，从而提供有关 XFEL 的 X 射线成像基础的关键信息。
X-ray free-electron lasers (XFELs) made available a new regime of x-ray intensities, revolutionizing the ultrafast structure determination and laying the foundations of the novel field of nonlinear x-ray optics. Although earlier studies revealed nanoplasma formation when an XFEL pulse interacts with any nanometer-scale matter, the formation process itself has never been decrypted and its timescale was unknown. Here we show that time-resolved ion yield measurements combined with a near-infrared laser probe reveal a surprisingly ultrafast population (similar to 12 fs), followed by a slower depopulation (similar to 250 fs) of highly excited states of atomic fragments generated in the process of XFEL-induced nanoplasma formation. Inelastic scattering of Auger electrons and interatomic Coulombic decay are suggested as the mechanisms populating and depopulating, respectively, these excited states. The observed response occurs within the typical x-ray pulse durations and affects x-ray scattering, thus providing key information on the foundations of x-ray imaging with XFELs.