Freiburg 2024 – scientific programme

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A: Fachverband Atomphysik

A 25: Poster IV

A 25.22: Poster

Wednesday, March 13, 2024, 17:00–19:00, Tent A

Probing resonant absorption in helium using intense XUV FEL pulses — •Arikta Saha¹, Alexander Magunia¹, Harijyoti Mandal¹, Muwaffaq Ali Mourtada¹, Carlo Kleine¹, Yu He¹, Marc Rebholz¹, Gergana D. Borisova¹, Hannes Lindenblatt¹, Florian Trost¹, Robert Moshammer¹, Stefan Düesterer², Tino Lang², Ulrike Fruehling², Christina Papadopoulou², Christina Böemer², Dietrich Krebs², Skirmantas Alisaukas², Christoph Heyl², Ingmar Hartl², Steffen Palutke², Markus Braune², Elisa Appi³, Doriana Vinci⁴, Milutin Kovacev⁵, Philip Mosel⁵, Peer Biesterfeld⁵, Christian Ott¹, and Thomas Pfeifer¹ — ¹Max-Planck-Institut für Kernphysik, 69117 Heidelberg, Germany — ²Deutsches Elektronen Synchrotron DESY, 22607 Hamburg, Germany — ³Lund University, 22100 Lund, Sweden — ⁴European XFEL, 22869 Schenefeld, Germany — ⁵Universität Hannover, 30167 Hannover, Germany

We studied excited state dynamics of helium using intense XUV FEL pulses. The XUV-driven nonlinear dynamics was measured by transient absorption spectroscopy. In the absorption spectrum, we look at 1s4p lineshape modifications in helium. The absorption lineshape is first excited by XUV pulses from high harmonic generation(HHG) and further modified by intense XUV FEL pulses, which leads to a change in the absorption feature. We observe absorption line shape modifications in the 1s4p line in time-resolved measurements on the femtosecond and picosecond timescale, as well as a function of FEL photon energy, FEL intensity, and helium target gas pressure.