Simon Marburger

Photoelectron circular dichroism in core level ionization of randomly oriented pure enantiomers of the chiral molecule camphor

The inner-shell photoionization of unoriented camphor molecules by circularly polarized light has been investigated from threshold to a photoelectron kinetic energy of approximately 65 eV. Photoelectron spectra of the carbonyl C 1s orbital, recorded at the magic angle of 54.7 degrees with respect to the light propagation direction, show an asymmetry of up to 6% on change of either the photon helicity or molecular enantiomer. These observations reveal a circular dichroism in the angle resolved emission with an asymmetry between forward and backward scattering (i.e., 0 degrees and 180 degrees to the light beam) which can exceed 12%. Since the initial state is an atomiclike spherically symmetric orbital, this strongly suggests that the asymmetry is caused by final-state effects dependent on the chiral geometry of the molecule. These findings are confirmed by electron multiple scattering calculations of the photoionization dynamics in the electric-dipole approximation.

Valence and C 1s core level photoelectron spectra of camphor

Abstract 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 ( h ν=357.9 eV) is also presented and reveals a marked shift of the carbonyl carbon relative to all others in the molecule.

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

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 discrimination of an electron pair.

A Molecular Beam Source for Electron Spectroscopy of Clusters

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.

A core-level photoionization study of furan

We have measured the vibrationally resolved C 1s photoelectron spectrum of the aromatic heterocycle furan (C4H4O). The vibrational profile appears to be dominated by a low-frequency mode, which shows an unusually high degree of excitation for ionization of the C atoms furthest from the oxygen. Our experimental results are compared with calculations, which reveal that several different vibrational modes participate in the vibrational pattern. A well resolved C 1s satellite spectrum at a photon energy of 335 eV has also been measured, and is compared to previous experimental and theoretical results. In a separate experiment the partial electron yield (“absorption”) spectrum has been obtained in the region from just below the C 1s π* resonance up to the respective ionization thresholds. A new high intensity feature has been identified on the high-energy flank of the C 1s−1π(3b1)* resonance. With the aid of resonant Auger spectroscopy we have tentatively assigned this feature to a Rydberg resonance. We also p...

Interface identification by non-local autoionization transitions.

We use an autoionization process that involves ultrafast energy transfer to neighbouring sites to characterize the formation of NeAr van der Waals bonds in clusters formed by a coexpansion of both gases. This autoionization process, the so-called interatomic or intermolecular coulombic decay (ICD), is ubiquitous in weakly bonded systems. The energy of the electron being emitted in the ICD process is shown to be characteristic of the two neighbouring entities and is therefore suggested as a new means for structural investigation, such as interface identification, of weakly bonded complexes.

VIBRATIONAL EXCITATION OF C 1s-IONIZED ETHANE

The effects of interaction between the vibrational and electronic structure, so-called vibronic coupling, are reviewed in the context of core-ionized states. High resolution C 1s spectra of ethane and deuterated ethane are used as an example to compare our reasoning with measurements.