Science@FELS

Experimental confirmation of reduced electronic damage during X-ray diffraction with attosecond pulses

23 Sept 2026, 19:30

1m

Auditorium (WHGA/001) (Paul Scherrer Institut)

Poster Poster Session (II)

Speaker

Dadian Guo (The University of Tokyo Graduate School of Frontier Sciences)

Description

Over the past decade, intense femtosecond X-ray pulses generated by XFELs have greatly advanced structure determination of radiation-sensitive samples through the “diffraction-before-destruction” approach. The ultrashort duration of XFEL pulses allows diffraction data to be collected before significant structural changes occur, thereby enabling determination of atomic structures beyond the conventional radiation-dose limit.

A remaining challenge in XFEL-based measurements is the mitigation of X-ray-induced electronic excitation. When an XFEL pulse interacts with matter, photoionization occurs during the pulse, followed by Auger decay shortly thereafter. The emitted electrons collide with surrounding atoms and ionize additional bound electrons, initiating a cascade of collisional ionization. As a result, a large number of valence electrons become excited on a femtosecond timescale. This electronic damage drives the sample away from its pristine state [1] and limits the realization of truly damage-free X-ray measurements.

Attosecond XFEL pulses have the potential to overcome this limitation and enable more precise structure determination. Since a delay of several hundred attoseconds exists between the initial photoionization event and the onset of collisional ionization [2], the use of attosecond pulses is expected to substantially suppress X-ray-induced electronic excitation [3]. To investigate the feasibility of electronically damage-free X-ray diffraction using attosecond pulses, we employed silicon (Si) as a model system and evaluated the extent to which attosecond XFEL pulses from SACLA suppress electronic excitation through measurements of the Si 222 “forbidden” reflection. This reflection arises primarily from the non-spherical distribution of valence electrons. Therefore, its diffraction intensity serves as a sensitive probe of X-ray-induced electronic damage.

In this presentation, we will show the intensity dependence of the Si 222 reflection measured with attosecond and femtosecond XFEL pulses at SACLA and discuss the implications of attosecond pulses for damage-free X-ray diffraction experiments.

[1] I. Inoue et al., Phys. Rev. Lett. 131, 163201 (2023).
[2] I. Inoue et al., Phys. Rev. Lett. 126, 117403 (2021).
[3] V. Lipp, I. Inoue, B. Ziaja, in preparation.