Abstracts

suchung von Sputterprozessen wird eine neue, zur Zeit im Aufbau befindliche, UHV-Apparatur vorgestellt.
Dies beinhaltet sowohl den geplanten Aufbau, als auch coupled-channel Rechnungen zur nicht-resonanten
Multiphotonenionisation von gesputterten Neutralteilchen.
Guido Saathoff, MPI Heidelberg
Improved test of relativistic time dilation by laser spectroscopy on fast ions
Heavy ion storage rings provide fast ion beams with very high spatial stability as well as low divergence.
This, together with modern techniques of high-resolution laser spectroscopy, constitutes the main ingredient
for a modern version of the classical Ives-Stilwell experiment, in which the relativistic Doppler formula
and, hence, the time dilation factor is tested by the measurement of a Doppler-shifted optical line. An
experiment at the TSR storage ring in Heidelberg employs saturation spectroscopy on a beam of singly
charged lithium ions at v=0.064c and improves the upper limit for deviations from special relativistic
time dilation by an order of magnitude. The present status as well as the investigation and control of
systematic errors are presented.
Cristina Sarpe-Tudoran, Uni Kassel
Adsorbtion of Hg on metal surfaces
The theoretical description of the adsorption on surfaces represent a big challenge especially when the
atoms involved are very heavy such that the relativistic effects play an important role. The adsorption of
Hg on different surfaces Pd, Pt and Au has been studied using a relativistic molecular program developed
in our group, which solves the relativistic Khon-Sham equations with the use of various density functionals.
To determine the adsorbtion geometry all the three possible position (top, bridge and hollow) of
the adsorbtion are considered.We present energy potential curve and the dissociation energy is compared
with the experimental value for Pd and Au surfaces.
Frank Scheuermann, Strahlenzentrum Uni Giessen
Elektronenstoßionisation hochgeladener Wismut-Ionen
F. Scheuermann, K. Huber, K. Kramer und E. Salzborn
Im Gießener crossed-beams Experiment wird momentan die Einfach- und Mehrfachionisation von Wismut-
Ionen durch Elektronenstoß untersucht. Die Messungen im Energiebereich bis 1keV sollen noch durch
Einbau einer Elektronenkanone für Energien bis 6,5keV ergänzt werden. Im Falle von Anteilen anderer
Ionen im Ionenstrahl mit annähernd gleichem Masse zu Ladungsverhältnis wird versucht, den Grad der
Verunreinigung zu bestimmen und den Wirkungsquerschnitt entsprechend zu korrigieren. Die Wirkungsquerschnitte
werden mit semiempirischen Formeln verglichen.
Thomas Schlathölter, KVI Groningen
Coulomb explosion of DNA bases
J. de Vries, R. Hoekstra, R. Morgenstern, T. Schlathölter
Modeling radiation damage on a macroscopic level has reached a high level of sophistication. However, for
a full understanding of the processes involved and for a realistic modeling the molecular pathways have to
be investigated on a microscopic level. Within the track of the primary radiation, hyperthermal electrons
as well as singly and multiply charged ions are formed. We studied the interaction of the latter with
RNA/DNA bases (uracil, thymine, guanine). From the flight-time differences of two correlated fragments
in coincidence with an emitted electron we obtained the kinetic energy release for particular dissociation
channels. For C q+ (q = 1 − 6) we found surprisingly high kinetic energies of the fragment ions as well
as unusual shapes of the islands in the coincidence plots. This indicates a two body Coulomb explosion
of the intermediate multiply charged molecules as a first step followed by extensive fragmentation of
these intermediates. To drive this processes to the extreme, electron removal and subsequent Coulomb
explosion of nucleobases driven by Xe q+ q = 5 − 25) was studied. Such very highly charged ions affect
the molecules quite similar as strong laser fields, i.e. short interaction time ( 10fs) as well as high electric
field ( 0.05 a.u.). It turns out, that the original location of the fragment within the molecule strongly
affects the corresponding coincidence patterns.
Michael Schnell, MPI Heidelberg
Experimentelle Beobachtung von trielektronischer Rekombination (TR)
Am Heidelberger Schwerionenspeichering TSR sind bei Elektron-Ion Rekombinationsexperimenten an
berylliumaehnlichen Ionen niederenergetische TR-Beitraege in den Rekombinationsspektren identifiziert
worden.
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