Impact of hollow-atom formation on coherent x-ray scattering at high intensity

Sang-Kil Son, Linda Young, and Robin Santra

[BibTeX]http://www.dpg-verhandlungen.de/year/2011/conference/dresden/part/a/session/26/contribution/15

X-ray free-electron lasers (FELs) are promising tools for structural determination of macromolecules via coherent x-ray scattering. The key obstacle for scattering imaging is radiation damage by ultraintense x-ray pulses. We develop a toolkit to treat detailed ionization, relaxation, and scattering dynamics for an atom within a consistent theoretical framework, and investigate the coherent x-ray scattering problem for a carbon atom including radiation damage. We find that the x-ray scattering intensity saturates at a high fluence but can be maximized by using a pulse duration much shorter than the relaxation time scales of the inner-shell vacancy states created. Under these conditions, both inner-shell electrons are removed, and the resulting hollow atom gives rise to a scattering pattern with little loss of quality for a desirable resolution. % for a spatial resolution > 1 Å. Our numerical results predict that in order to scatter from a carbon atom 0.1 photons per x-ray pulse, within a spatial resolution of 1.7 Å, a fluence of 10⁷ photons/Ų per pulse is required at a pulse length of 1 fs and a photon energy of 12 keV. By using a pulse length of a few hundred attoseconds, one can suppress even secondary ionization processes in extended systems. The present results suggest that high-brightness attosecond x-ray FELs would be ideal for single-shot imaging of individual macromolecules.

Tags: hollow-atom, damage, ionization, Auger, fluorescence, x-ray scattering, x-ray diffraction, molecular imaging, FEL, C, CFEL, DESY, DPG