Following the Birth of a Nanoplasma Produced by an Ultrashort Hard-X-Ray Laser in Xenon Clusters

Abstract

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 (∼12 fs), followed by a slower depopulation (∼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.

Core-level interatomic Coulombic decay in van der Waals clusters

“…However, since noble gas clusters are commonly used as prototype systems in studies on interaction of matter with ionizing radiation, the direct nonlocal decay of core vacancies may have immediate implications. Especially in the emerging field of x-ray imaging with high-intensity free electron laser (FEL) radiation, processes like core-level ICD have not yet been considered to contribute to charge distribution and nanoplasma formation [28,29]. Here, we unambiguously demonstrate the occurrence of core-level ICD in van der Waals systems by presenting an observation of these processes in 2p core-ionized Ar clusters.…”

X-ray induced ultrafast dynamics in atoms, molecules, and clusters: experimental studies at an X-ray free-electron laser facility SACLA and modelling

“…Furthermore, various levels of experimental methods and theoretical modelling are within reach for these relatively simple targets. Because of these reasons, atoms [6][7][8][9][10][11], molecules [12][13][14][15][16][17][18][19][20], and atomic clusters [21][22][23][24][25][26][27][28] irradiated by an XFEL pulse have been investigated extensively.…”

“…In this article, we review our experiments at SACLA, an XFEL facility in Japan, during the first five years, and modelling efforts, studying the interaction between intense, short X-ray pulses and gas-phase targets of increasing complexity, from atoms [8,11] to molecules [15][16][17]19,20] and to atomic clusters [24][25][26][27][28]. The main goal of these studies is to gain some insight into the interaction of the intense pulse with the single-particle targets, to understand if and how they are modified within the pulse duration.…”

Mapping ultrafast ionization of atoms and clusters with terahertz-streaking delay

“…When a nanoscale system is hit by an intense FEL pulse, complex electron and nuclear dynamics evolve on time scales from a few femtoseconds to several hundreds of picoseconds [14][15][16]. While the processes evolving in the nanoscale system after the FEL pulse has ended are accessible in the time domain by one-or twocolor pump-probe techniques [17][18][19][20][21][22], time-resolved studies covering time scales shorter than the FEL pulse duration remain challenging [23]. A technique capable of accessing these time scales is light-field streaking that is sensitive to the time instance at which an electron is freed into the continuum [24][25][26].…”