  The influences of water molecules surrounding biological molecules during
irradiation with heavy particles (atoms,ions) are currently a major subject in
radiation science on a molecular level. In order to elucidate the underlying
complex reaction mechanisms we have initiated a joint experimental and
theoretical investigation with the aim to make direct comparisons between
experimental and theoretical results. As a first step, studies of collisions of
a water molecule with a neutral projectile (C atom) at high velocities (> 0.1
a.u.), and with a charged projectile (proton) at low velocities (< 0.1 a.u.)
have been studied within the microscopic framework. In particular,
time-dependent density functional theory (TDDFT) was applied to the valence
electrons and coupled non-adiabatically to Molecular dynamics (MD) for ionic
cores. Complementary experimental developments have been carried out to study
projectile interactions with accelerated (< 10 keV) and mass-selected cluster
ions. The first size distributions of protonated water cluster ions H+(H_2O)_n
(n=2-39) produced using this new apparatus are presented.

Atomic and Molecular Clusters