Hamburg 2009 – wissenschaftliches Programm
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A: Fachverband Atomphysik
A 34: Poster II
A 34.2: Poster
Donnerstag, 5. März 2009, 16:30–19:00, VMP 9 Poster
Auto-detaching multi-electron superexcited state in free C60 anions probed by photoelectron spectroscopy — •Mattias Svanqvist and Bernd von Issendorff — University of Freiburg
In photoelectron spectra of C60− irradiated by nanosecond laserpulses, evidence of electron Auger-like auto-detachment processes have previously been observed. To gain insight into the origin of this feature we have conducted a detailed study by investigating the photoelectron spectra for a photon energy range range of 3.8 to 4.8 eV. We observe a linear dependence of the peak position in the binding energy spectra on the photon energy as expected for auto-detachment, which allows us to determine the excitation energy of the autodetaching state as about 3.5 eV. The large photon energy range over which the feature is observable indicates a relaxation to a common state from which the auto detachment occurs. DFT calculations show that there is indeed a gap in the density of excited states in this energy region. Moreover, we have measured a red shift in the kinetic energy of the auto-detached electrons with increasing temperature. With a simple semi-empirical model we show that this shift is linear in the vibrational energy. An offset between the shifts of two different wavelengths supports a picture where the system transforms excess photon energy into vibrational energy before auto-detachment.