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Atomic Physics

Faculty of Engineering, LTH

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Ultrafast X-ray science

In our research, we are applying ultrafast time-resolved X-ray probes as tools in solid-state physics and chemistry. This type of work will yield understanding of how light induced processes change the structure of matter.

The dynamic properties of solids couple to atomic motion and the relevant time-scale is that of a vibrational period, which is approximately equal to 100 femtoseconds (0.0000000000001 seconds). This is the time scale on which molecular dynamics, chemical reactions and phase transitions in solids occur. In contrast with existing, femtosecond laser probes, X-rays have a wavelength approximately equal to the distances between atoms, and hence enable atomic movements to be visualised directly. Thus, the natural technique for studying evolving atomic structures is through X-ray diffraction. Since their discovery, X-rays have been the dominant tool for determining atomic structures. We believe that the availability of time-resolved structural probes with sub-picosecond time-resolution which employ X-ray diffraction, would enable groundbreaking work by allowing the interrogation of rapidly changing structures. However, the lack of both ultrashort-pulse X-ray sources and ultrafast x-ray detectors has, until very recently, prevented such studies. During recent years a rapid development of pulsed X-ray sources has been achieved, falling into two main categories: Laser-based table top sources; and sources based on partice accelerations (for example synchtrotrons). Currently these activities are pursued in collaboration with research groups worldwide in order to utilise existing X-ray sources coupled to femtosecond laser facilities. In the medium term (5-10 years), it is clear that the field will be driven by what can be achieved in terms of developing sources. Our work involves both source development and applied science.