Femtosecond Reduction of Atomic Scattering Factors Triggered by Intense X-Ray Pulse

X-ray diffraction of silicon irradiated with tightly focused femtosecond x-ray pulses (photon energy, 11.5 keV; pulse duration, 6 fs) was measured at various x-ray intensities up to 4.6×1019 W/cm2. The measurement reveals that the diffraction intensity is highly suppressed when the x-ray intensity reaches of the order of 1019 W/cm2. With a dedicated simulation, we confirm that the observed reduction of the diffraction intensity can be attributed to the femtosecond change in individual atomic scattering factors due to the ultrafast creation of highly ionized atoms through photoionization, Auger decay, and subsequent collisional ionization. We anticipate that this ultrafast reduction of atomic scattering factor will be a basis for new x-ray nonlinear techniques, such as pulse shortening and contrast variation x-ray scattering.Received 13 April 2023Revised 18 August 2023Accepted 28 August 2023DOI:https://doi.org/10.1103/PhysRevLett.131.163201© 2023 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasUltrafast phenomenaPhysical SystemsFree-electron lasersWarm-dense matterTechniquesX-ray powder diffractionAtomic, Molecular & OpticalPlasma PhysicsAccelerators & Beams