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Title: Decreasing ultrafast x-ray pulse durations with saturable absorption and resonant transitions

Journal Article · · Physical Review. E

Saturable absorption is a nonlinear effect where a material's ability to absorb light is frustrated due to a high influx of photons and the creation of electron vacancies. Experimentally induced saturable absorption in copper revealed a reduction in the temporal duration of transmitted x-ray laser pulses, but a detailed account of changes in opacity and emergence of resonances is still missing. In this computational work, we employ nonlocal thermodynamic equilibrium plasma simulations to study the interaction of femtosecond x rays and copper. Following the onset of frustrated absorption, we find that a K–M resonant transition occurring at highly charged states turns copper opaque again. The changes in absorption generate a transient transparent window responsible for the shortened transmission signal. We also propose using fluorescence induced by the incident beam as an alternative source to achieve shorter x-ray pulses. Intense femtosecond x rays are valuable to probe the structure and dynamics of biological samples or to reach extreme states of matter. Shortened pulses could be relevant for emerging imaging techniques.

Research Organization:
Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
Sponsoring Organization:
USDOE National Nuclear Security Administration (NNSA); Swedish Research Council (SRC); Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)
Grant/Contract Number:
AC52-07NA27344; 2019-03935; 2018- 00740
OSTI ID:
1909713
Alternate ID(s):
OSTI ID: 1969162
Report Number(s):
LLNL-JRNL-845838; PLEEE8; 015205
Journal Information:
Physical Review. E, Journal Name: Physical Review. E Vol. 107 Journal Issue: 1; ISSN 2470-0045
Publisher:
American Physical SocietyCopyright Statement
Country of Publication:
United States
Language:
English

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