When silicon crystals are lit up with ultrafast laser pulses of X-ray light, the resulting diffraction images are certainly at first brighter the more photons fall on the sample, i.e., the higher the beam strength.
X-ray free-electron lasers (XFELs) generate very powerful X-ray pulses with durations of femtoseconds, i.e., quadrillionths of a second. The observation that different atoms react differently to ultrafast X-ray pulses may assist to more properly reconstruct three-dimensional complex atomic structures from the recorded diffraction images.
Another area of prospective application has to do with the production of laser pulses with exceptionally short pulse durations. Given that the material through which the high-intensity X-ray pulse passes cuts off a significant part of the currently ultra-short pulse, it can be deliberately utilized as scissors to create pulses that are efficiently much shorter than those produced so far.
Experimental set-up at the SACLA facility used for the presented diffraction experiment on crystalline silicon samples. Credit: SACLA
Unexpected Observations in X-ray Diffraction
The more light, the better? This observation may sound minor, were it not for the truth that … it is not constantly real! When silicon crystals are brightened with ultrafast laser pulses of X-ray light, the resulting diffraction images are indeed initially brighter the more photons fall on the sample, i.e., the higher the beam intensity.
Just recently, nevertheless, a counterproductive effect has actually been observed: when the strength of the X-ray beam begins to surpass a specific critical value, the diffraction images all of a sudden deteriorate.
This perplexing phenomenon has just been described, thanks to the efforts of the speculative and theoretical physicists from Japanese, Polish and German research study institutions, including the RIKEN SPring-8 Centre in Hyogo, the Institute of Nuclear Physics of the Polish Academy of Sciences (IFJ PAN) in Cracow and the Center for Free-Electron Laser Science (CFEL) at the DESY laboratory in Hamburg.
The SACLA free-electron laser center, where the experiment on the diffraction of ultra-short X-ray pulses on crystalline silicon samples was performed. Credit: SACLA
The Role of XFELs in Matter Analysis
X-ray free-electron lasers (XFELs) produce really effective X-ray pulses with durations of femtoseconds, i.e., quadrillionths of a second. With this method, a sample is brightened by an X-ray pulse and the diffracted radiation is taped.
Describing the Unexpected Dimming Effect
” Intuition informs us that the more photons we have, the clearer the diffraction picture of the sample need to be. This is undoubtedly the case, but only approximately a particular X-ray intensity, of the order of 10s of trillions of watts per square centimeter. When this value is gone beyond– and we have actually been just recently capable of doing this– the diffraction signal suddenly starts to deteriorate. Our research study is the very first attempt to explain this unanticipated impact,” states Prof. Beata Ziaja-Motyka (IFJ PAN, DESY), who handles theoretical modeling and computer simulations of phenomena connected to the interaction of ultrafast X-ray pulses with matter.
Insights From Theoretical Research and Simulations
Theoretical research carried out to discuss the outcomes of the explore XFEL laser shooting on crystalline silicon samples at Japans XFEL facility, called SACLA, Hyogo, has actually been supported by computer system simulations. The following explanation of the phenomenon observed emerged from the researchers work.
” When an avalanche of high-energy photons strikes a material, there is a huge knockout of electrons from different atomic shells, leading to a rapid ionization of atoms in the material. Last year, our group revealed that the first movements of ionized atoms in the crystal lattice, initiating the procedure of structural self-destruction of the sample, accompanied a delay of approximately 20 femtoseconds after the light pulse struck the sample. We are now convinced that the reason for the just recently observed weakening of the diffraction signal is due to phenomena occurring earlier, in the first six femtoseconds of the interaction,” says Dr. Ichiro Inoue from the RIKEN SPring-8 Centre, responsible for the experimental research study.
During the preliminary stage of X-ray-matter interaction, incoming high-energy photons quickly thrilled not just surface area (valence) electrons from atoms, however likewise the electrons occupying deep atomic shells, situated near to the atomic nucleus. It ends up that the presence of deep shell holes in atoms strongly decrease their atomic scattering factors, i.e., the amounts figuring out the strength of the observed diffraction signal.
Electronic Damage and Its Effects
” Our research reveals that before any structural damage to the material takes place and the sample disintegrates, initially a rapid electronic damage takes place. As a result, the final part of the pulse virtually no longer ionizes the product, because more excitation of electrons by X-ray photons is no longer energetically possible,” Prof. Ziaja-Motyka specifies.
Potential Applications and Breakthroughs
At first glance, the observed impact appears to be just unfavorable, as it results in a reduced brightness of the diffraction images recorded. It appears that one can really well exploit this finding. The observation that various atoms respond differently to ultrafast X-ray pulses may help to more properly reconstruct three-dimensional complex atomic structures from the taped diffraction images.
Another area of prospective application pertains to the production of laser pulses with exceptionally short pulse periods. Given that the product through which the high-intensity X-ray pulse passes cuts off a substantial part of the already ultra-short pulse, it can be intentionally used as scissors to create pulses that are successfully shorter than those produced up until now. If successful, this could promote another advancement in the imaging of the quantum world.
Reference: “Femtosecond Reduction of Atomic Scattering Factors Triggered by Intense X-Ray Pulse” by Ichiro Inoue, Jumpei Yamada, Konrad J. Kapcia, Michal Stransky, Victor Tkachenko, Zoltan Jurek, Takato Inoue, Taito Osaka, Yuichi Inubushi, Atsuki Ito, Yuto Tanaka, Satoshi Matsuyama, Kazuto Yamauchi, Makina Yabashi and Beata Ziaja, 17 October 2023, Physical Review Letters.DOI: 10.1103/ PhysRevLett.131.163201.
The research provided here was co-financed by the Institute of Nuclear Physics of the Polish Academy of Sciences.
A global research partnership discovered that ultrafast X-ray laser pulses trigger silicon crystals diffraction images to dim at high intensities due to quick electronic damage. This discovery opens brand-new possibilities for much shorter laser pulse production and more precise atomic structure analysis.
Research study exposes that high-intensity X-ray pulses cause unforeseen dimming in silicon crystal diffraction images, a phenomenon that might cause advancements in laser technology and product analysis.
When we light up something, we typically expect that the brighter the source we utilize, the brighter the resulting image will be. This guideline also works for ultra-short pulses of laser light– but only up to a particular intensity.
Researchers are exploring why X-ray diffraction images end up being less brilliant at very high X-ray intensities. Understanding this phenomenon not only deepens our knowledge of light-matter interaction but also offers a distinct perspective for the production of laser pulses with much shorter periods than those presently offered.
