T1: Nanoscale imaging and spectroscopy with soft X-rays
Imaging with soft X-rays combines high spatial resolution (< 50 nm) with unique
contrast mechanisms, such as spectroscopic and magnetic contrast, and high
penetration depth. In addition, the time structure of the X-ray sources enables
time-resolved imaging with picosecond down to femtosecond temporal resolution.
The key issue of X-ray imaging is to efficiently solve the phase problem, i. e., the
loss of the scattered wave's phase information upon detection. We particularly
employ (and further develop) three different methods: numerical iterative phase
retrieval from a coherent diffraction pattern, interference with a reference wave
(holography), and full-field microscopy using a refractive X-ray lens.
Bastian Pfau, Holger Stiel
T2: Femtosecond X-ray diffraction and absorption
In a pump-probe approach, photo-induced structure changes in the femtosecond
time domain are studied by diffracting ultrashort hard X-ray pulses from the
excited sample. Both changes of atomic arrangements, i.e. lattice geometries, and
of electronic charge density are addressed. The measurement of transient electron
density maps has been pioneered by MBI and requires the simultaneous detection
of many diffraction peaks. Femtosecond powder diffraction and the rotation
method for single crystals have been implemented to fulfill this requirement.
Michael Wörner, Christoph Hauf