Mainz 2026 – scientific programme

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MO: Fachverband Molekülphysik

MO 4: Novel Experimental Approaches and Novel Theoretical and Computational Approaches

MO 4.1: Invited Talk

Monday, March 2, 2026, 17:00–17:30, P 105

A two-color glimpse at nanomatter: ultrafast movies coming soon. — •Alessandro Colombo, Linos Hecht, and Daniela Rupp for the TwoColorCDI collaboration — ETH Zurich, Switzerland

Pairs of ultrashort, ultrabright X-ray pulses of distinct wavelengths can now be produced by X-ray Free Electron Lasers (XFELs) [1]. The possibility of precisely controlling their time delay down to the femtosecond regime allows for probing the same system at two different points in time, even down to the natural timescales of electron dynamics. In this talk, we describe how two-color pulses can be combined with diffraction imaging experiments [2], to capture two time-delayed snapshots of a sample and track its light-induced ultrafast changes. In particular, we show results on two-color diffraction patterns acquired at the European XFEL, where two images of the same sample, separated in time by 750 fs, are successfully reconstructed despite the challenging experimental conditions [3]. While improvements on both the instrument and the analysis sides are still necessary to maximize the resolution of the technique, the exciting possibility of two-color diffraction imaging at XFELs, so far considered unviable, opens a new research path for tracking in space and time ultrafast structural and electron dynamics in nanomatter. The long-standing dream of capturing ultrafast movies of nanomatter with an XFEL is finally at hand, along with a new class of experiments yet to be explored.

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[1] S. Serkez et al., Applied Sciences 10, 2728 (2020)
[2] L. Hecht et al., arXiv:2508.19991 (2025), in review at Nat Commun
[3] L. Hecht et al., arXiv:2508.20153 (2025), in review at Nat Commun

Keywords: Ultrafast imaging; Coherent Diffraction Imaging; X-ray Free Electron Laser