  Ion energy distributions arising from laser-produced plasmas of Sn are
measured over a wide laser parameter space. Planar-solid as well as
liquid-droplet targets are exposed to infrared laser pulses with energy
densities between 1J/cm$^2$ and 4kJ/cm$^2$ and durations spanning 0.5ps to 6ns.
The measured ion energy distributions are compared to two self-similar
solutions of a hydrodynamic approach assuming isothermal expansion of the
plasma plume into vacuum. For planar and droplet targets exposed to ps-long
pulses we find a good agreement between the experimental results and the
self-similar solution of a semi-infinite simple planar plasma configuration
with an exponential density profile. The ion energy distributions resulting
from solid Sn exposed to ns-pulses agrees with solutions of a limited-mass
model that assumes a Gaussian-shaped initial density profile.
