X-ray lasers bring us into a new world in photon science by delivering
extraordinarily intense beams of x-rays in very short bursts that can
be more than ten billion times brighter than pulses from other x-ray
sources. These lasers find applications in sciences ranging from
astrophysics to structural biology, and could allow us to obtain
images of single macromolecules when these are injected into the x-ray beam.
A macromolecule injected into vacuum in a microdroplet will be affected by
evaporation and by the dynamics of the carrier liquid before being hit
by the x-ray pulse. Simulations of neutral and charged water droplets
were performed to predict structural changes and changes of temperature
due to evaporation. The results are discussed in the aspect of single molecule
imaging.
Further studies show ionization caused by the intense x-ray radiation.
These simulations reveal the development of secondary electron cascades
in
water. Other studies show the development of these cascades in
KI and
CsI where experimental data exist. The results are in agreement with
observation, and show the temporal, spatial and energetic evolution
of secondary electron cascades in the sample.
X-ray diffraction is sensitive to structural changes on the length
scale of chemical bonds. Using a short infrared pump pulse to trigger
structural changes, and a short x-ray pulse for probing it, these
changes can be studied with a temporal resolution similar to the
pulse lengths. Time resolved diffraction experiments were performed on
a phase transition during resolidification of a non-thermally molten
InSb
crystal. The experiment reveals the dynamics of crystal regrowth.
Computer simulations were performed on the infrared laser-induced
melting of bulk ice, giving a comprehension of
the dynamics and
the wavelength dependence of melting.
These studies form a basis for planning experiments with x-ray lasers.
Full pdf avaidable from the university home page.
