Darmstadt 2008 – scientific programme

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A: Fachverband Atomphysik

A 10: Posters: Atomic clusters

A 10.7: Poster

Tuesday, March 11, 2008, 16:30–18:30, Poster C3

Angularly resolved photoelectron spectroscopy of Na clusters: Simple models — •Jan Huwer, Christof Bartels, Christian Hock, and Bernd v.Issendorff — Fakultät für Mathematik und Physik, Universität Freiburg, Stefan-Meier-Str. 21, 79104 Freiburg

Measurements of angularly resolved photoelectron spectra of negatively charged free sodium clusters (n=19…147) with ns-laser pulses (λ=290…755 nm) have been performed.

Energy-resolved photoelectron spectra of sodium clusters can be explained in the framework of the so-called Jellium model in most cases. In this model, the experimentally observed shell structure is explained by assuming that the atomic valence electrons can be treated as particles in an effective single-particle potential. The question is whether this one-particle picture also holds for excitation processes. If this was the case, the angular distributions could be calculated in analogy to one-electron atoms as shown by Bethe. The shape of the angular distributions can be reduced to one asymmetry parameter β, which only depends on the radial transition matrix elements and the scattering phases of the outgoing partial waves.

By assuming single-particle potentials of box and Woods-Saxon type, β parameters have been calculated for the experimentally investigated states. As observed in the experiment, the angular distributions show a strong dependence on the excitation energy. Furthermore we identified some general characteristics of the angular distributions for different orbital momentum states.