Experimental demonstration of attosecond hard X-ray pulses
preprint
posted on 2025-06-11, 16:00 authored by Ichiro Inoue, River Robles, Aliaksei Halavanau, Veronica Guo, Thomas M. Linker Andrei Benediktovitch, Stasis Chuchurka, Matthew H. Seaberg, Yanwen Sun, Diling Zhu, David Cesar, Yuantao Ding, Vincent Esposito, Paris Franz, Nicholas S. Sudar, Zhen Zhang, Taito Osaka, Gota Yamaguchi, Yasuhisa Sano, Kazuto Yamauchi, Jumpei Yamada, Uwe Bergmann, Matthias F. Kling, Claudio Pellegrini, Makina Yabashi, Nina Rohringer, Takahiro Sato, Agostino MarinelliWe present the first direct experimental confirmation of attosecond pulse generation in the hard X-ray regime with a free-electron laser. Our experiment is based on measurements of a nonlinear optical phenomenon known as amplified spontaneous emission (ASE) from 3d transition metals. By analyzing the yield of the collective X-ray fluorescence induced by ultrashort pulses at the Linac Coherent Light Source, we identify the generation of attosecond pulses and shot-to-shot fluctuations in their duration, ranging from 100 as to 400 as. The observed product of bandwidth and pulse duration for 100 as pulses is approximately 2 fs$\cdot$eV, indicating the generation of nearly transform-limited pulses. Our results extend the photon energy reach of attosecond techniques by one order of magnitude, providing the ability to simultaneously probe matter on the time-scales of electronic phenomena and with atomic spatial resolution. Furthermore, attosecond hard X-ray pulses can outrun the fastest radiation damage processes, paving the way to single-shot damage-free X-ray measurements.
