# Osnabrück 2002 – wissenschaftliches Programm

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# MO: Molekülphysik

## MO 15: Photoionisation II (gemeinsam mit FV Atomphysik)

### MO 15.7: Vortrag

### Donnerstag, 7. März 2002, 15:30–15:45, HS 15/E10

**High-resolution photoelectron emission from oriented N**_{2}** molecules** — •Rainer Hentges^{1}, Daniel Rolles^{1}, Georg Prümper^{1}, Alexander Golovin^{2}, and Uwe Becker^{1} — ^{1}Fritz-Haber-Institut der MPG, Faradayweg 4-6, 14195 Berlin, Germany — ^{2}Petersburg State University, Institute of Physics, Petrodvorets, 198904 St. Petersburg, Russia

Photoionization of homonuclear molecules, in particular of their
innermost 1*s* shells, is a showcase of the coherent superposition
of
photoelectron waves from two spatially separated atomic sites.
There is a very successful approximation of
core level photoelectron and Auger electron emission, the
*one center approximation*, which considers
the electron emission as being strongly localized.
The resulting electron angular distribution is therefore
calculated as an incoherent sum of electron waves emitted from
both
atomic sites.
On the other hand, there is evidence for a splitting of
the 1*s* photoelectron lines into *gerade* and
*ungerade* components [1],
a clear signature of delocalized and coherent electron
emission.
However, model calculations show that if the two components
are not resolved, the photoelectron angular distributions in the
molecule frame are the same for both cases.
Therefore only a high resolution measurement of the molecule
frame angular distribution can distinguish between these two
models.
We have performed such an experiment for N_{2} at beamline
BW3 of HASYLAB.
The results are presented and discussed with respect
to the coherence properties of the emitted N_{2}: N(1*s*)
photoelectrons.

[1] U. Hergenhahn et al., J. Phys. Chem. A
**105**, 5704 (2001).