![]() It is this process that takes about 20 femtoseconds. However, the atoms themselves, hitherto electrically inert, become strongly electrically charged and begin to feel repulsion from their similarly charged neighbors. Due to the significant mass difference between the released electrons and the ionizing atoms, the latter do not initially feel the recoil. As a result of this interaction, electrons are massively knocked out of the atoms. When photons of high energy enter the crystal, they transmit this energy mainly to the electrons in the atoms embedded in the nodes of the crystal lattice. The delayed response of oxygen and aluminum atoms in corundum to the X-ray pulse turns out to be a consequence of the following course of events. "We believe that the main reason for this delay is the fact that the electrons located in atoms trapped in the nodes of the crystal lattice act a bit like a bumper and are the first to take up the impetus of the X-ray pulse," adds Dr. Victor Tkachenko (IFJ PAN), was involved in the theoretical description and simulations of the phenomena studied. "The experimental results are in excellent agreement with the predictions of our models and simulations, where a similar delay also appears," says Prof. The data collected allowed us to estimate that the crystal atoms start to react to the photon beam with a delay of 20 femtoseconds," says Dr. In our research with corundum nanocrystals, we used pulses lasting just six femtoseconds. "A unique feature of our laser is its ability to produce pulses of hard-that is, high-energy-X-rays that are both ultra-short and of a high intensity. The experimental part was carried out using the SACLA X-ray laser operating in Hyogo, Japan. In their latest paper, appearing in Physical Review Letters, the scientists present the results of work on processes such as these in the case of corundum nanocrystals made up of oxygen and aluminum atoms. The group has been studying the interaction of laser X-ray pulses with matter for several years. ![]() Ichiro Inoue of Japan's RIKEN SPring-8 Center FEL facility. Ziaja-Motyka is a member of an international team of experimental and theoretical physicists led by Dr. ![]() Beata Ziaja-Motyka of the Institute of Nuclear Physics of the Polish Academy of Sciences (IFJ PAN) in Cracow and the Centre for Free-Electron Laser Research (CFEL) at DESY in Hamburg. So what do we see in the diffraction images recorded-the true structure of the sample or rather an image of its destruction?" asks Prof. "When we irradiate a sample with lots of high-energy photons, its atoms begin to interact with the radiation so strongly that the material is destroyed. In this approach, however, there lurks a very serious problem. After irradiating a sample with such a pulse, a diffraction image is produced, from which physicists can attempt to reconstruct the spatial structure of the molecules. Lasers of this type are capable of generating X-ray pulses with unique qualities: not only are they ultra-short, measured in single femtoseconds, but they also contain a great many photons. Is it possible to see chemical reactions of complex molecules at subatomic resolution? It seems so, but only with the use of free electron lasers (FEL).
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