2010- @DESY

XMOLECULE: molecular black hole

XMOLECULE is a computational toolkit for simulating electronic and nuclear dynamics induced by x-rays. Electrons are treated quantum mechanically and nuclear motions are solved classically. Based on the Hartree-Fock-Slater method, XMOLECULE solves the Schrödinger equations for calculating electronic structure of multiple-core-hole states that may be formed during interaction with intense x-ray pulses. To achieve an efficient way of calculating molecular core-hole states, it employs numerical atomic orbitals as basis functions, which are optimized for respective atomic core-hole states [1]. For rate and cross section calculations, it utilizes atomic continuum states [2]. In other words, XMOLECULE takes full advantages of XATOM to perform electronic structure and ionization dynamics calculations. During time evolution, xmolecule can handle electronic dynamics among highly excited states created by x-rays, hopping back and forth between potential energy surfaces separated by a few hundreds eV and keV. For nuclear dynamics, XMOLECULE solves the Newton equations based on molecular gradients calculated on-the-fly. These electronic dynamics and nuclear dynamics are coupled to each other and treated together with different time scales via a Monte Carlo on-the-fly approach.

XMOLECULE was applied to quantitatively describe the XFEL–molecule interaction for the first time. We presented a joint experimental and theoretical study of small polyatomic molecules irradiated by ultra-intense hard X-rays, capturing a detailed picture of ultrafast ionization and fragmentation dynamics of molecules [3]. The unprecedentedly high-intensity x-rays knock out lots of electrons from a molecule, creating a sort of molecular black hole as depicted in the figure. It sucks electrons away from neighboring atoms and ejects them furthermore, resulting in significant ionization enhancement for molecules. We named this new phenomenon as CREXIM (charge-rearrangement-enhanced x-ray ionization of molecules) and it provides new insights for understanding the process of radiation damage at high x-ray intensity and designing future XFEL experiments. This story of molecular black hole has been highlighted by the media as the followings:

The extremely intense X-ray flash knocks so many electrons out of the iodine atom (right) such that it pulls in the electrons of the methyl group (left) like an electromagnetic version of a black hole, before finally spitting them out. Credit: DESY/Science Communication Lab.

Related Publications
  1. Yajiang Hao, Ludger Inhester, Kota Hanasaki, Sang-Kil Son, and Robin Santra, Efficient electronic structure calculation for molecular ionization dynamics at high x-ray intensity, Struct. Dyn. 2, 041707 (2015) [special issue on biology with x-ray lasers 2] [bib][BibTeX][pdf][pdf][abstract][abstract][link]doi:10.1063/1.4919794
  2. Ludger Inhester, Kota Hanasaki, Yajiang Hao, Sang-Kil Son, and Robin Santra, X-ray multiphoton ionization dynamics of a water molecule irradiated by an x-ray free-electron laser pulse, Phys. Rev. A 94, 023422 (2016) [bib][BibTeX][pdf][pdf][abstract][abstract][link]doi:10.1103/PhysRevA.94.023422
  3. Artem Rudenko, Ludger Inhester, Kota Hanasaki, Xiang Li, Seyyed J. Robatjazi, Benjamin Erk, Rebecca Boll, Koudai Toyota, Yajiang Hao, Oriol Vendrell, Cedric Bomme, Evgeny Savelyev, Benedikt Rudek, Lutz Foucar, Stephen H. Southworth, Carl S. Lehmann, Bertold Krässig, Tatiana Marchenko, Marc Simon, Kiyoshi Ueda, Ken R. Ferguson, Maximilian Bucher, Tais Gorkhover, Sebastian Carron, Roberto Alonso-Mori, Jason E. Koglin, Jonathan Correa, Garth J. Williams, Sébastien Boutet, Linda Young, Christoph Bostedt, Sang-Kil Son, Robin Santra, and Daniel Rolles, Femtosecond response of polyatomic molecules to ultra-intense hard X-rays, Nature 546, 129–132 (2017) [bib][BibTeX][abstract][abstract][link][link][link]doi:10.1038/nature22373
  4. Julia M. Schäfer, Ludger Inhester, Sang-Kil Son, Reinhold F. Fink, and Robin Santra, Electron and fluorescence spectra of a water molecule irradiated by an x-ray free-electron laser pulse, Phys. Rev. A 97, 053415 (2018) [bib][BibTeX][pdf][pdf][abstract][abstract][link]doi:10.1103/PhysRevA.97.053415
  5. Ludger Inhester, Bart Oostenrijk, Minna Patanen, Esko Kokkonen, Stephen H. Southworth, Christoph Bostedt, Oksana Travnikova, Tatiana Marchenko, Sang-Kil Son, Robin Santra, Marc Simon, Linda Young, and Stacey L. Sorensen, Chemical understanding of the limited site-specificity in molecular inner-shell photofragmentation, J. Phys. Chem. Lett. 9, 1156–1163 (2018) [bib][BibTeX][abstract][abstract][link]doi:10.1021/acs.jpclett.7b03235
Oral Presentations
Multiphoton multiple ionization dynamics of atoms and molecules at high x-ray intensity by Sang-Kil Son
  1. International Workshop on Intense-field Short-wavelength Atomic and Molecular Processes (Hamburg, Germany, July 18-20, 2015) [invited talk] [bib][BibTeX][slide][slide: 4Mb][abstract][abstract][link][link]
  2. 4th CFEL Symposium 2015 (CFEL, Timmendorfer Strand, Germany, September 30-October 2, 2015) [oral presentation] [bib][BibTeX]
  3. The 47th Meeting of the Division of Atomic, Molecular and Optical Physics (American Physics Society, Providence, Rhode Island, May 23-27, 2016) [invited talk] [bib][BibTeX][abstract][abstract][link][link]
  4. The electronic-structure problem in theoretical strong-field physics (ITAMP, Harvard University, Cambridge, Massachusetts, October 10-14, 2016) [invited talk] [bib][BibTeX][link][link]
  5. Korean Physical Society Fall Meeting (Korean Physical Society, Gwangju, Korea, October 19-21, 2016) [invited talk] [bib][BibTeX][abstract][abstract][link][link]
  6. Workshop on Science of “From Matter to Materials and Life” (Hamburg, Germany, December 14-16, 2016) [oral presentation] [bib][BibTeX][abstract][abstract][link][link]
  7. New trends in theory for experiments at advanced light sources (European XFEL and CFEL, Schenefeld and Hamburg, Germany, November 29-December 1, 2017) [invited talk] [bib][BibTeX][link][link]
  8. The 7th Topical Conference of the Indian Society of Atomic and Molecular Physics (Indian Society of Atomic and Molecular Physics, Tirupati, India, January 6-8, 2018) [invited talk] [bib][BibTeX][pdf][pdf][abstract][abstract][link][link]
  9. Light-Matter Interaction: Recent Advances in Theory (DESY, Hamburg, Germany, January 25, 2018) in Satellite Workshop of European XFEL and DESY Photon Science Users' Meeting 2018 [invited talk] [bib][BibTeX][link][link]
What happens to atoms and molecules during x-ray free-electron laser pulses? by Sang-Kil Son
  1. Seminar on Dynamical Aspects of Theoretical Chemistry (Free University of Berlin, Berlin, Germany, November 19, 2015) [invited talk] [bib][BibTeX][abstract][abstract]
  2. Physical Colloquium (Institute of Physics, University of Kassel, Kassel, Germany, December 3, 2015) [invited talk] [bib][BibTeX][pdf][pdf][abstract][abstract]
  3. Physics and Photon Science Colloquium (Gwangju Institute of Science and Technology, Gwangju, Korea, October 18, 2016) [invited talk] [bib][BibTeX][slide][slide: 15Mb][abstract][abstract][link][link]
  4. European XFEL Theory Seminar (European XFEL, Schenefeld, Germany, June 22, 2017) [invited talk] [bib][BibTeX][abstract][abstract][link][link]