TY  - JOUR
A1  - Navirian, Hengameh A.
A1  - Herzog, Marc
A1  - Goldshteyn, J.
A1  - Leitenberger, Wolfram
A1  - Vrejoiu, Ionella
A1  - Khakhulin, D.
A1  - Wulff, M.
A1  - Shayduk, Roman
A1  - Gaal, P.
A1  - Bargheer, Matias
T1  - Shortening x-ray pulses for pump-probe experiments at synchrotrons
JF  - Journal of applied physics
N2  - We implemented an experimental scheme for ultrafast x-ray diffraction at storage rings based on a laser-driven Bragg-switch that shortens the x-ray pulses emitted from an undulator. The increased time-resolution is demonstrated by observing changes of intensity, position and width of the diffraction peaks of a La(0.7)Sr(0.3)MnO(3)/SrTiO(3) superlattice sample after optical excitation, i.e., by quantitatively measuring the propagation of an expansion wave through the sample. These experimental transients with timescales of 35 to 60 ps evidence a reduction of the x-ray pulse duration by a factor of two.
Y1  - 2011
U6  - https://doi.org/10.1063/1.3601057
SN  - 0021-8979
VL  - 109
IS  - 12
PB  - American Institute of Physics
CY  - Melville
ER  - 
TY  - JOUR
A1  - Shayduk, Roman
A1  - Navirian, Hengameh
A1  - Leitenberger, Wolfram
A1  - Goldshteyn, Jevgenij
A1  - Vrejoiu, Ionela
A1  - Weinelt, Martin
A1  - Gaal, Peter
A1  - Herzog, Marc
A1  - von Korff Schmising, Clemens
A1  - Bargheer, Matias
T1  - Nanoscale heat transport studied by high-resolution time-resolved x-ray diffraction
JF  - New journal of physics : the open-access journal for physics
N2  - We report on synchrotron-based high-repetition rate ultrafast x-ray diffraction (UXRD) experiments monitoring the transport of heat from an epitaxial La(0.7)Sr(0.3)MnO(3)/SrTiO(3) superlattice (SL) into the substrate on timescales from 100 ps to 4 mu s. Transient thermal lattice expansion was determined with an accuracy of 10(-7), corresponding to a sensitivity to temperature changes down to 0.01 K. We follow the heat flow within the SL and into the substrate after the impulsive laser heating leads to a small temperature rise of Delta T = 6 K. The transient lattice temperature can be simulated very well using the bulk heat conductivities. This contradicts the interpretation of previous UXRD measurements, which predicted a long-lasting expansion of SrRuO(3) for more than 200 ps. The disagreement could be resolved by assuming that the heat conductivity changes in the first hundred picoseconds.
Y1  - 2011
U6  - https://doi.org/10.1088/1367-2630/13/9/093032
SN  - 1367-2630
VL  - 13
IS  - 11
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Kiel, Mareike
A1  - Möhwald, Helmuth
A1  - Bargheer, Matias
T1  - Broadband measurements of the transient optical complex dielectric function of a nanoparticle/polymer composite upon ultrafast excitation
JF  - Physical review : B, Condensed matter and materials physics
N2  - We determined experimentally the complex transient optical dielectric function of a well-characterized polyelectrolyte/gold-nanoparticle composite system over a broad spectral range upon short pulse laser excitation by simultaneously measuring the time-dependent reflectance and transmittance of white light pulses with femtosecond pump-probe spectroscopy. We extracted directly the ultrafast changes in the real and imaginary parts of the effective dielectric function, epsilon(eff)(r) (omega,t)and epsilon(eff)(i) (omega,t), from the experiment. This complete experimental set of information on the time-dependent complex dielectric function challenges theories modeling the transient dielectric function of gold particles and the effective medium.
Y1  - 2011
U6  - https://doi.org/10.1103/PhysRevB.84.165121
SN  - 1098-0121
VL  - 84
IS  - 16
PB  - American Physical Society
CY  - College Park
ER  -