International Research Fellowship Program: Laser-Based Femtosecond X-Ray Development and Application

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0502281ShahThe International Research Fellowship Program enables U.S. scientists and engineers to conduct three to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad.This award will support a twenty-two-month research fellowship by Dr. Rahul C. Shah to work with Dr. Antoine Rousse at the Laboratoire Optique Appliquee in Palaiseau, France.In a little over 100 years, x-rays have become one of the most powerful tools scientists have for peering into atomic scale structures. Among the various techniques, x-ray spectroscopy obviates the need for crystals, a requirement which severely limits range of studies for such atomic visualization. This work pushes x-ray science into dynamical studies of molecules at timescales of hundreds of femtoseconds by (1) developing an ultra-fast, directional, and broadband x-ray source from ultra-intense laser pulses and (2) utilizing it to identify femtosecond rearrangements in a chemical reaction by x-ray spectroscopy. The host site is where laser researchers have developed a 100 Terawatt, 10 Hz laser, and the work will be done in collaboration with Antoine Rousse and the Femtosecond X-ray Physics group, pioneers in the field of ultrafast x-ray source development and diffraction studies. The research more specifically studies the source spectrum by use of crystal spectrometer, and this is correlated with electron beam characteristics as well as plasma density, controlled by the density of the injected helium gas. Chemistry, biology, and solid state physics are all disciplines which have relied on x-rays for identification of molecular structures. Optical studies have indicated that systems in each of these disciplines evolve at femtosecond timescales but do not provide the structural details of x-rays. Thus this bright source of ultrafast x-rays which is of university laboratory scale stands to have far reaching impact. Demonstration of the usefulness of the source for quantitative x-ray absorption spectroscopy will introduce a valuable new tool, with advantages unique from diffraction techniques, to ultrafast x-ray studies.