Grain Nucleation Experiments and Other Laboratory Data
  In order to interpret observations influenced by dust and to perform detailed
modeling of the observable characteristics of dust-producing or dust-containing
objects, knowledge of the micro-physical properties of relevant dust species
are needed. Laboratory measurements of cosmic dust analogues provides essential
input for our understanding of how dust particles can influence the dynamics
and thermodynamics of the stellar atmosphere by their opacity. The formation of
the dust grains influences the stellar atmosphere in two ways. In the gas phase
chemistry, dust formation results in a depletion of certain elements, which
influences the molecular composition of the gas and consequently the
corresponding opacities. On the other hand, dust grains have a rather high mass
absorption coefficient, which often may be comparable to the gas opacity or
even exceed it. Due to its high opacity and the resulting radiative pressure,
the dust has a strong influence on the structure of the atmosphere and the wind
properties of AGB stars. Great care is needed when obtaining laboratory data as
even a moderate variation of the different micro-physical dust values within
the range expected for possible materials has noticeable consequences for the
interpretation of the near-infrared colors of AGB stars.
