Augsburg 2006 – wissenschaftliches Programm

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K: Kurzzeitphysik

K 5: Licht- und Strahlungsquellen

K 5.5: Vortrag

Dienstag, 28. März 2006, 12:15–12:30, 1003

Femtosecond X-ray diffraction at the SPPS: Direct observation of coherent optical phonons in laser-excited Bismuth. — •Matthieu Nicoul¹, David Fritz², Aaron Linderberg³, Patrick Hillyard⁴, Simon Endemann³, Juana Rudati⁵, David Reis², Kelly Gaffney³, Jerome Hastings³, Klaus Sokolowski-Tinten¹, and Dietrich von der Linde¹ — ¹Institut für Experimentelle Physik, Universität Duisbug-Essen, Lotharstr. 1, 47048 Duisburg, Germany — ²FOCUS Center, Departments of Physics and Applied Physics Program, University of Michigan, Ann Harbor, MI 48109, USA — ³Stanford Synchrotron Radiation Laboratory/SLAC, Menlo Park, CA 94025, USA — ⁴Department of Chemistry, Stanford University, Stanford, CA 94305, USA — ⁵Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, USA

The Sub-Picosecond Pulse Source (SPPS) at the Stanford Linear Accelerator Center is the first operating accelerator-driven ultrafast hard X-ray source worldwide and represents a precursor for the future X-ray free electron laser LCLS. Bunches of electrons delivered by the linear accelerator in Stanford are accelerated to 27 GeV, are compressed and then are sent through an undulator to generate a well-collimated X-ray beam with 10^7 photons per pulse of less than 100 fs duration. The photon energy is tunable around 9 keV. These ultrashort X-ray pulses were used to study coherent optical phonons in femtosecond laser-excited Bismuth by means of time-resolved diffraction. The experimental data reveal a strong decrease of the phonon frequency and allow a quantitative determination of the vibrational amplitude and the atomic displacements.