Oliver Kugeler - Profile on Academia.edu (original) (raw)

Papers by Oliver Kugeler

A Molecular Beam Source for Electron Spectroscopy of Clusters

AIP Conference Proceedings, 2004

ABSTRACT We describe the construction and testing of a supersonic jet apparatus to carry out elec... more ABSTRACT We describe the construction and testing of a supersonic jet apparatus to carry out electron spectroscopy on Van-der-Waals clusters using Synchrotron Radiation as an excitation source. The cluster source works with a conical nozzle that can be cooled with LHe as well as with LN2. The system has been optimized for mechanical and thermal stability, for low residual magnetic fields and is of a compact design.

Photo-and Auger electron angular distributions of nitrogen molecules fixed in space

ABSTRACT Molecule frame electron angular distribution in the gas phase have attracted increasing ... more ABSTRACT Molecule frame electron angular distribution in the gas phase have attracted increasing interest during the last five years after the first of such distributions was measured [1]. The studies were extended over a variety of molecules and performed for core ionization as well as valence ionization [2, 3]. Experimentally such studies are measurements of vector correlations between the emission directions of electrons and fragment ions produced via the photoionization or -excitation process. The corresponding angular distribu-tions provide a wealth of information on the dynamics of molecular photoionization, in particular dipole transition matrix elements and their corresponding phases. Some of these experiments are expected to be sensitive to the coherence properties of the photoemission process in the case of homonuclear molecules, a problem closely related to the core-hole localization [4-6]. We have performed two types of experi-ments of this subject, one concerned with the ejection of a 1s photoelectron of N 2 in the vicinity of the σ shape resonance and the other exploring the Auger angular distributions after photoexcitation of N 2 to the π* resonance. Both experiments are intended to shed some light on the problem to which extend core holes in N 2 are localized or delocalized. The experiments were performed at beamline BW3 using an angle resolved fragment-ion-electron coincidence setup. This setup consists of a ion time-of-flight spectrometer having position sensitive anode combined with five independent electron time-of-flight spectrometers in order to allow for the angle resolved detection of both particles in coincidence [3].

The Journal of Physical Chemistry A, 2001

Inner-shell photoelectron spectra of the N 1s level in N 2 have been measured with sufficient res... more Inner-shell photoelectron spectra of the N 1s level in N 2 have been measured with sufficient resolution to resolve the splitting between the gerade and ungerade components. The selective enhancement of the gerade component on the N 2 σ shape resonance is clearly seen, confirming that the resonant behavior is mainly caused by the σ u channel. The splitting of the two components is found to be 97(3) meV.

Calculation and measurement of the time-of-flight spread in a hemispherical electron energy analyzer

Review of Scientific Instruments, 2003

We have determined the transit time distribution of electrons passing a high resolution hemispher... more We have determined the transit time distribution of electrons passing a high resolution hemispherical energy analyzer. Comparison of our measured results with analytical expressions reveals that differing transit times between electrons of equal kinetic energy mainly build up on the Kepler-type orbits on which the electrons travel through the hemispheres. To facilitate the measurements, we have installed a position sensitive electron detector capable of single event detection into our spectrometer. This device is based on a delay-line anode. We briefly report on the energy resolution achieved in comparison with a slower readout system via a fluorescent screen. The transit time distribution is important in coincidence experiments, where electrons detected in the hemispherical analyzer are to be related to events in other detectors. We discuss the feasibility of electron–electron coincidence experiments using a hemispherical detector plus a time-of-flight drift tube for energy discrim...

Journal of Physics: Conference Series, 2012

Journal of Physics: Conference Series, 2009

Journal of Electron Spectroscopy and Related Phenomena, 2002

The valence photoelectron spectrum of camphor has been recorded with 95 eV synchrotron radiation,... more The valence photoelectron spectrum of camphor has been recorded with 95 eV synchrotron radiation, with better definition than previous He I spectra. The spectrum is interpreted by comparison with these He I results and with the aid of an outer-valence Green's Function calculation of the orbital ionization energies. These calculations closely reproduce the observed vertical ionization energies in the outer valence region. A core level spectrum of the C 1s region (hn5357.9 eV) is also presented and reveals a marked shift of the carbonyl carbon relative to all others in the molecule.

Chemical Physics, 2006

In this article, we demonstrate that Interatomic Coulombic Decay (ICD) is the dominant relaxation... more In this article, we demonstrate that Interatomic Coulombic Decay (ICD) is the dominant relaxation channel of Ne 2s inner valence vacancies in free Ne clusters, with an efficiency close to 100 %. ICD designates a novel autoionization process of a vacancy in a weakly bonded atomic or molecular cluster. Its main characteristic is the release of an electron from a site different than the original vacancy, which is mediated by ultrafast energy transfer. Results are shown for cluster sizes between approx. 50-600 atoms. A trend towards apparently increased efficiency for larger clusters may result from inelastic scattering processes inside the cluster.

Photoelectron - Auger-electron coincidence measurements in N2O K-shell photoionisation