Free-electron lasers produce extremely brief, coherent, and bright laser-like photon pulses
that allow to image matter at atomic resolution and at timescales faster than the …

Femtosecond laser pulses have proven to provide valuable insight into the dynamics of
microscopic systems by using pump–probe techniques. Applied to atomic clusters even a …

In the spectral range of the extreme ultraviolet at a wavelength of 13.3 nm, we have studied
the photoionization of xenon at ultrahigh intensities. For our ion mass-to-charge …

We have developed different types of photodetectors that are based on the photoionization
of a gas at a low target density. The almost transparent devices were optimized and tested …

A simple, analytical, nonrelativistic ionization rate formula for atoms and positive ions in
intense ultraviolet and x-ray electromagnetic fields is derived. The rate is valid at arbitrary …

Multi-electron dynamics in atoms and molecules very often occur on sub-to few-femtosecond
time scales. The available intensities of extreme-ultraviolet (XUV) attosecond pulses have …

A theory describing above-threshold ionization of atoms and ions in a strong
electromagnetic field is presented. It is based on the widely known strong field …

In contrast to the long-wavelength regime, x-ray nonlinear optical processes are
characterized in general by sequential single-photon single-electron interactions. Despite …

Few-photon multiple ionization of Ne and Ar atoms by strong vacuum ultraviolet laser pulses
from the free-electron laser at Hamburg was investigated differentially with the Heidelberg …

At the soft-x-ray free-electron laser FLASH in Hamburg, we have studied multiphoton
ionization on neon and helium by ion mass-to-charge spectroscopy. The experiments were …