Non-Adiabatic Quantum Molecular Dynamics:
   Competing Reaction Mechanisms in Atom-Cluster Collisions

   Ulf Saalmann a) and Rüdiger Schmidt b)

   a) Atomfysik, Stockholms Universitet,
      Frescativägen 24, 10405 Stockholm, Sweden

   b) Institut für Theoretische Physik,
      Technische Universität, 01062 Dresden, Germany

 Atom-cluster collisions are studied by means of a simultaneous and
self-consistent treatment of 
 electronic and atomic degrees of freedom involved.  We examine the
excitation mechanisms (electronic
 versus vibrational) and the related relaxation phenomena (phase
transitions, fragmentation)  for impact 
 energies from eV to MeV. "Cluster  transparency" is found in a small
window of energies. In addition, 
 the charge transfer competing with fragmentation in collisions with
sodium clusters is investigated.