Berlin 2014 – wissenschaftliches Programm

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A: Fachverband Atomphysik

A 30: Interaction with VUV and X-ray light I

A 30.1: Hauptvortrag

Mittwoch, 19. März 2014, 14:00–14:30, BEBEL E42

Stimulated electronic x-ray Raman scattering using x-ray free-electron lasers — •Nina Rohringer — Max Planck Institute for the Physics of Complex Systems, 01187 Dresden — Center for Free-Electron Laser Science, 22761 Hamburg

X-ray free-electron lasers (XFELs) open the pathway to transfer non-linear spectroscopic techniques to the x-ray domain, to study the interplay of electronic and vibrational degrees of freedom by time-domain spectroscopy. A promising all x-ray pump probe technique is based on coherent electronic x-ray Raman scattering. I will present the first experimental demonstration of stimulated electronic x-ray Raman scattering. By tuning the relatively broad XFEL pulses to the core-excited Rydberg resonances in the pre K-edge region of neon, resonance scattered photons drive an avalanche of inelastic x-ray scattering events, resulting in exponential amplification of the scattering signal by 6-7 orders of magnitude. Analysis of the line profile of the emitted radiation permits to demonstrate the cross over from amplified spontaneous emission to coherent resonance scattering: In case of coherent scattering, the emitted x-ray radiation shows a pulse-to-pulse fluctuation of the line shape and the spectral peak position, resulting from a stochastic detuning of spectrally structured XFEL pulses from resonance. In combination with statistical covariance mapping, a high-resolution spectrum of the resonant inelastic x-ray scattering process can be obtained, opening the path to coherent stimulated x-ray Raman spectroscopy. An extension of these ideas to molecules will be discussed.