Hannover 2010 – wissenschaftliches Programm
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A: Fachverband Atomphysik
A 28: Attosecond Physics II / Interaction with Strong or Short Laser Pulses III
A 28.3: Vortrag
Freitag, 12. März 2010, 14:30–14:45, F 107
Quasi-elastic electron scattering from atoms and molecules — Adam P. Hitchcock1, Glyn Cooper1, Russ A. Bonham2, and •Aris C. C.-Dreismann3 — 1Brockhouse Institute for Materials Research, McMaster University, Hamilton, ON, L8S 4M1, Canada — 2Department of Biological, Chemical and Physical Sciences, Illinois Institute of Technology, Chicago, Illinois 60616, USA — 3Institute of Chemistry, Sekr. C2, Technical University of Berlin, D-10623 Berlin
We have measured quasi-elastic electron scattering spectra from molecules and atoms at large momentum transfer Q (100 deg. angle, 2.25 keV incident energy, Q~20 a.u.). The peak positions agree completely with those predicted by classical conservation of momentum and energy, assuming the electron scatters from each atom independently. However the peak intensities do not agree with expectations, particularly for light elements. According to classical electron Compton scattering, quasi-elastic peak intensities should be propotional to nuclear charge squared. However, our recent study [1] found a significant deviation (~30%) in the intensities of the H versus D signals relative to this prediction. Here we present new quasi-elastic electron scattering data for H2/D2, Ar/H2, Ar/D2, He/H2 and Ar/He mixtures [2]. Large deviations from conventional theoretical expectations are obserded, for all samples. The possible connection of this striking effect with decoherence and the quantum Zeno effect is shortly mentioned.
[1] G. Cooper et al., PRL 100, 043204 (2008). [2] A. P. Hitchcock et al., J. Electron Spectrosc. Relat. Phenom., in press (2010)