Plenarvorträge - DPG-Tagungen

Oberflächenphysik Mittwoch
and electronic properties are observed. In contrast to silver islands grown
on germanium (001) the orientation of the crystal lattice is not fixed if
cluster melting is neglected. However, some of the clusters show hexagonal
facets at the top. STS is sensitive to occupied and unoccupied states
near the Fermi level and reveals the existence of distinct states in the
tunneling conductivity of the substrate as well as on the clusters. Thus,
the richly structured density of states of the germanium (001) surface
has been discovered and serves as STM/STS condition test.
O 28.69 Mi 16:00 Bereich C
Application of the variable phase theory to the systems with
quasistationary states. — •Oleg Kidun 1 , Jamal Berakdar 1 ,
and Natasha Fominykh 2 — 1 Max-Planck Institut fuer Mikrostrukturphysik,
Halle, Germany — 2 Institute of Physics, St. Petersburg State
University, St. Petersburg, Russia
We develop a method of investigation of the quasistationary (QS)
states of different physical systems based on the variable phase approach
[1-3]. We consider the modification of the physical properties of the QS
states (energy position and resonance width) under the spatial transformation
of the potential field as well as its asymptotical behavior. The
role of the possible nonlocality of the potential in the observability of
the QS states is also estimated. The realization of our approach in the
studies of molecules and nanostructures is discussed.
[1] F. Calogero, Variable Phase Approach in Potential Scattering, AP,
NY (1967)
[2] V. Babikov, Method of the Phase Functions in Quantum Mechanics,
Nauka, Moscow (1969)
[3] O. Kidun, N. Fominykh, J. Berakdar, J. Phys. A 35, 9413 (2001)
O 28.70 Mi 16:00 Bereich C
Electron dynamics of buried interface states in Ar/Cu(100)
probed by time-resolved two-photon photoemission — •M.
Rohleder, W. Berthold, K. Duncker, J. Güdde, and U.
Höfer — Fachbereich Physik und Zentrum für Materialwissenschaften,
Philipps-Universtät, D-35032 Marburg
We demonstrate for the system Ar/Cu(100) how in favourable cases the
dynamics of electronic states located at the interface between a metal and
an insulator can be investigated by means of time-resolved two-photon
photoemission (2PPE). The interface states of Ar/Cu are located above
the vacuum level in the band gaps of both the Cu(100) surface and the
Ar films which were as thick as 70 monolayers (ML). With increasing
layer thickness the states evolve from quantum-well-like resonances into
well-defined bound states which arise from the screened image-potential
of the metal. Electrons excited into these states decay on timescales between
100 fs and 250 fs by electron-hole pair excitation in the metal and
– for thin Ar layers (