Ultrafast X-rays or ultrashort X-ray pulses are femtosecond x-ray pulses with wavelengths occurring at interatomic distances. This beam uses the X-ray's inherent abilities to interact at the level of atomic nuclei and core electrons. This ability combined with the shorter pulses at 30 femtosecond could capture the change in position of atoms, or molecules during phase transitions, chemical reactions, and other transient processes in physics, chemistry, and biology.^[1][2]

Ultrafast X-ray diffraction (time-resolved X-ray diffraction) can surpass ultrashortpulse visible techniques, which are limited to detecting structures on the level of valence and free electrons. Ultrashort pulse X-ray techniques are able to resolve atomic scales, where dynamic structural changes and reactions occur in the interior of a material.^{[3][4] [5] [6]}

• Stanford PULSE Institute for ultrafast x-ray science
• Ultrafast laser spectroscopy

• Emma P., et al. (2010) "First lasing and operation of an angstrom-wavelength free-electron laser" Nature Photonics 4(9):641-647.
• Philip H. Bucksbaum; Ryan Coffee; Nora Berrah (2011). "The First Atomic and Molecular Experiments at the Linac Coherent Light Source X-Ray Free Electron Laser". In E. Arimondo; P.R. Berman; C.C. Lin (eds.). Advances in Atomic, Molecular, and Optical Physics. Advances In Atomic, Molecular, and Optical Physics. Vol. 60. Academic Press. pp. 239–289. Bibcode:2011AAMOP..60..239B. doi:10.1016/B978-0-12-385508-4.00005-X. ISBN 9780123855084.
• Diagram of the table-top ultrafast X-ray diffractometer

Rose-Petruck, Christoph; et al. (March 25, 1999). "Figure 1". Nature. 398 (6725): 310–312. Bibcode:1999Natur.398..310R. doi:10.1038/18631. S2CID 4399550.

• Figures and Tables. Nature Publishing Group. March 25, 1999.

• Photon Science: X-Rays for Discovery
• Ultrafast X-ray Summer Schools