Ultrafast X-ray laser-induced explosion: How the depth influences the direction of the ion trajectory

¹ Department of Chemistry – BMC, Uppsala University - Box 576, SE-751 23 Uppsala, Sweden
² Department of Physics and Astronomy, Uppsala University - Box 516, SE-751 20 Uppsala, Sweden
³ Department of Physics and INFN, University of Rome Tor Vergata - I-00133 Rome, Italy
⁴ European XFEL - Holzkoppel 4, DE-22869 Schenefeld, Germany
⁵ Center for Free-Electron Laser Science CFEL, Deutsches Elektronen-Synchrotron DESY - Notkestraße 85, DE-22607 Hamburg, Germany

Received: 28 February 2024
Accepted: 9 September 2024

Abstract

Single particle imaging using X-ray lasers is a technique aiming to capture atomic resolution structures of biomolecules in their native state. Knowing the particle's orientation during exposure is crucial for method enhancement. It has been shown that the trajectories of sulfur atoms in a Coulomb exploding lysozyme are reproducible, providing orientation information. This study explores if sulfur atom depth influences explosion trajectory. Employing a hybrid collisional-radiative/molecular dynamics model, we analyze the X-ray laser-induced dynamics of a single sulfur ion at varying depths in water. Our findings indicate that the ion spread-depth relationship depends on pulse parameters. At a photon energy of 2 keV, high-charge states are obtained, resulting in an increase of the spread with depth. However, at 8 keV photon energy, where lower charge states are obtained, the spread is essentially independent with depth. Finally, lower ion mass results in less reproducible trajectories, opening a promising route for determining protein orientation through the introduction of heavy atoms.