Giving to CREOL CREOL, The College of Optics & Photonics

Seminar: "Resonant nonlinear ultrafast dynamics in atoms and molecules driven by an intense XUV free-electron laser" by Dr. Christian Ott

Friday, June 22, 2018 1:30 PM to 2:30 PM
CREOL Room 103

Dr. Christian Ott
Max Planck Institute for Nuclear Physics
Heidelberg, Germany


In this talk I will report on our recent activities of all-optical transient absorption spectroscopy with XUV light from the Free Electron Laser at Hamburg (FLASH). We have experimentally investigated resonant transitions in atoms and small molecules that are exposed to intense (pulse energies up to 50 µJ and duration on the order of 50 fs) laser pulses in the XUV (50 eV / 60 eV). With this method we are sensitive to the onset of strong-field XUV effects which manifest in significant changes of the measured absorption line shapes. Making use of the partial coherence of the self-amplified spontaneous emission (SASE) properties of the FEL, we were also able to observe a coherent enhancement on the time-scale of a few femtoseconds across the pump–probe temporal overlap. The physics accessed within this scheme are both cooperative multi-electron transitions (e.g. two-electron transitions in helium), as well as spin-orbit multiplet transitions in transiently generated open-shell atoms (e.g. valence transitions in Ne2+). The combined spectro-temporal sensitivity of this approach, i.e., to resolve and identify distinct spectral signatures of multi-electron transitions in the XUV together with its element specific access to inner-shell dynamics at an ultrafast femtosecond timescale, opens up new avenues to be explored for the investigation of correlated electron dynamics in the presence of strong XUV electric fields.


Christian Ott received his PhD in 2012 from Heidelberg University on attosecond interferometric techniques and strong-field control of two-electron dynamics, working in the independent research group of Prof Thomas Pfeifer at MPIK. He has spent two years as a postdoc with Profs Stephen Leone and Daniel Neumark, working on attosecond transient absorption spectroscopy of strongly correlated materials at the University of California at Berkeley, USA, sponsored by a Feodor Lynen postdoctoral fellowship of the Alexander von Humboldt foundation. Since 2016 he is appointed staff scientist and group leader at the Max Planck Institute for Nuclear Physics in Heidelberg, Germany, in the Quantum Dynamics and Control division of Prof Thomas Pfeifer. His research activities include the experimental investigation of few-electron dynamics in natural many-electron systems (mainly gas phase atoms and molecules), investigated with strong and ultrashort (femtosecond to attosecond) laser pulses. One key tool that is applied in his group is attosecond transient absorption spectroscopy, to observe and understand tiny changes in spectral line shapes (asymmetric Fano converted to symmetric Lorentzian) that are associated to a laser-controlled manipulation of correlated electron dynamics. Very recently these activities have been extended to intense XUV light from free-electron lasers.

For additional information:
Dr. Zenghu Chang

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