Femtosecond-resolved observation of the fragmentation of buckminsterfullerene following X-ray multiphoton ionization

Nora Berrah, Alvaro Sanchez-Gonzalez, Zoltan Jurek, Razib Obaid, Hui Xiong, Richard J. Squibb, Timur Osipov, Alberto Lutman, Li Fang, Thomas Barillot, John D. Bozek, James Cryan, Thomas J.A. Wolf, Daniel Rolles, Ryan Coffee, Kirsten Schnorr, Sven Augustin, Hironobu Fukuzawa, Koji Motomura, N. Niebuhr, Leszek J. Frasinski, Raimund Feifel, Claus P. Schulz, Koudai Toyota, Sang-Kil Son, Kiyoshi Ueda, Thomas Pfeifer, Jon P. Marangos, and Robin Santra

[BibTeX]doi:10.1038/s41567-019-0665-7

X-ray free-electron lasers have, over the past decade, opened up the possibility of understanding the ultrafast response of matter to intense X-ray pulses. In earlier research on atoms and small molecules, new aspects of this response were uncovered, such as rapid sequences of inner-shell photoionization and Auger ionization. Here, we studied a larger molecule, buckminsterfullerene (C₆₀), exposed to 640 eV X-rays, and examined the role of chemical effects, such as chemical bonds and charge transfer, on the fragmentation following multiple ionization of the molecule. To provide time resolution, we performed femtosecond-resolved X-ray pump/X-ray probe measurements, which were accompanied by advanced simulations. The simulations and experiment reveal that despite substantial ionization induced by the ultrashort (20 fs) X-ray pump pulse, the fragmentation of C₆₀ is considerably delayed. This work uncovers the persistence of the molecular structure of C₆₀, which hinders fragmentation over a timescale of hundreds of femtoseconds. Furthermore, we demonstrate that a substantial fraction of the ejected fragments are neutral carbon atoms. These findings provide insights into X-ray free-electron laser-induced radiation damage in large molecules, including biomolecules.

Tags: C60, XMDYN, experiment, pump-probe, fragmentation, ultrafast, LCLS, CFEL, DESY