Suppression of thermal nanoplasma emission in clusters strongly ionized by hard x-rays

Yoshiaki Kumagai (1, 2) , Zoltan Jurek (3) , Weiqing Xu (4) , Vikrant Saxena (3) , Hironobu Fukuzawa (5) , Koji Motomura (5) , Denys Iablonskyi (5) , Kiyonobu Nagaya (6) , Shin-Ichi Wada (6) , Yuta Ito (5) , Tsukasa Takanashi (7) , Shuhei Yamada (7) , Yuta Sakakibara (7) , Toshiyuki Nishiyama Hiraki (8) , Takayuki Umemoto (9) , Minna Patanen (10) , John Bozek (10) , Ioan Dancus (11) , Mihail Cernaianu (11) , Catalin Miron (12) , Tobias Bauer (13) , Melanie Mucke (14) , Edwin Kukk (15) , Shigeki Owada (16) , Tadashi Togashi (17) , Kensuke Tono (17) , Makina Yabashi (16) , Sang-Kil Son (3) , Beata Ziaja (3) , Robin Santra (3) , Kiyoshi Ueda (5)

1 Institute for Materials Research, Tohoku University
2 TUAT - Tokyo University of Agriculture and Technology
3 CFEL - Center for Free-Electron Laser Science
4 University of Shanghai for Science and Technology
5 Institute of Multidisciplinary Research for Advanced Materials
6 RIKEN SPring-8 - Center Soft X-Ray Spectroscopy Instrumentation Team [Hyogo]
7 Institute of Multidisciplinary Research for Advanced Materials
8 DEPARTMENT OF PHYSICS, KYOTO UNIVERSITY - Department of Physics, Kyoto University
9 Graduate School of Advanced Science and Engineering [Higashi-Hiroshima]
10 SSOLEIL - Synchrotron SOLEIL
11 ELI-NP - Extreme Light Infrastruture - Nuclear Physics
12 LIDyl - Laboratoire Interactions, Dynamiques et Lasers (ex SPAM)
13 Institut für Kernphysik [Frankfurt]
14 Uppsala University
15 University of Turku
16 RIKEN RSC - RIKEN SPring-8 Center [Hyogo]
17 JASRI - Japan Synchrotron Radiation Research Institute [Hyogo]

Using electron and ion spectroscopy, we studied the electron and nuclear dynamics in ~50 000-atom large krypton clusters, following excitation with an intense hard x-ray pulse. Beyond the single pulse experiment, we also present the results of a time-resolved, x-ray pump–near-infrared probe measurement that allows one to learn about the time evolution of the system. After core ionization of the atoms by x-ray photons, trapped Auger and secondary electrons form a nanoplasma in which the krypton ions are embedded, according to the already published scenario. While the ion data show expected features, the electron emission spectra miss the expected pump–probe delay-dependent enhancement except for a slight enhancement in the energy range below 2 eV. Theoretical simulations help to reveal that, due to the deep trapping potential of the ions during the long time expansion accompanied by electron–ion recombination, thermal emission from the transient nanoplasma becomes quenched.

Domains: Mechanics of materials [physics.class-ph]; Physics [physics]

Yoshiaki Kumagai, Zoltan Jurek, Weiqing Xu, Vikrant Saxena, Hironobu Fukuzawa, et al.. Suppression of thermal nanoplasma emission in clusters strongly ionized by hard x-rays. Journal of Physics B: Atomic, Molecular and Optical Physics, 2021, 54 (4), pp.044001. ⟨10.1088/1361-6455/abd878⟩. ⟨cea-03191956⟩