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O: Fachverband Oberflächenphysik

O 43: Poster Session II - MA 141/144 (Surface Spectroscopy on Kondo Systems; Frontiers of Surface Sensitive Electron Microscopy; Methods: Scanning Probe Techniques+Electronic Structure Theory+Other; Time-Resolved Spectroscopy of Surface Dynamics with EUV and XUV Radiation; joined by SYNF posters)

O 43.40: Poster

Dienstag, 26. Februar 2008, 18:30–19:30, Poster F

Influence of Laser Heating on the X-ray Diffraction Intensity of InSb — •Jessica Walkenhorst, Eeuwe S. Zijlstra, and Martin E. Garcia — Theoretische Physik, Fachbereich Naturwissenschaften, Universität Kassel, Heinrich-Plett-Str. 40, 34132 Kassel

Hillyard et al. have measured the x-ray diffraction intensity of the (111) peak of InSb after intense laser excitation, which provides insight in the first stages of laser-induced ultrafast melting. They found that the diffraction peak follows a Gaussian decay. This time-dependence has been analyzed using the Debye model for the atomic vibrations, assuming the laser heating to produce a uniform softening of all phonon frequencies. We performed (i) first principle electronic structure calculations, (ii) molecular dynamic simulations to calculate the phonon frequencies at the Γ-, X- and L-point and the resulting x-ray intensity. We found, that dramatic phonon softening does not occur at all the investigated k-points but instead the softening of the transverse acoustic phonons at the X-point suffices to explain the measured Gaussian x-ray intensity decay and perfectly reproduces the decay’s measured time constant.