Exploring damage reduction and scattering cross section enhancement in attosecond X-ray imaging of neon near the K-edge

Ultrafast X-ray coherent diffraction imaging combines nanometer spatial resolution with few to sub-femtosecond temporal precision. In a diffraction before diffraction scheme, ultrabright FEL pulses are scattered by the sample before it's ionic structure is substantially modified. It has been suggested in theoretical studies that the induced sample damage can be reduced if the pulses are much shorter than the relaxation processes, such as Auger decay [Rohringer et al., Phys. Rev. A 77, 053404].

Using the newly available XLEAP technique [Duris et al., Nat. Photonics 14, 30–36], we performed single-exposure X-ray diffraction experiments on individual neon nanoparticles around the K-edge at the TMO beamline at the LCLS. We have compared images recorded with ~18 fs pulses to snapshots captured with sub-fs pulses, which are shorter than the 3 fs life time of the K-shell core hole. The coincident ion spectra mirrored the ionization degree and thus, damage to the nanoparticle illuminated by the FEL. We observe an irradiance-dependent increase in scattering cross section near the K-edge, hinting towards transient resonance effects. At the same time, the XLEAP pulses seem to cause less damage than the 18 fs pulses with similar fluence. Preliminary results and possible explanations for the impacts of photon flux and pulse duration will be discussed.