Environmental molecular beam studies of ice surface processes
Paper i proceeding, 2011
The development and application of a new molecular beam setup for studies of gas-ice interactions at pressures
in the 0.001 mbar range is described. Direct simulation Monte Carlo calculations have been applied to optimize
the experimental design with respect to gas transmission through the high pressure zone outside the ice surface
and pressure along the surface plane. In a first application of the new setup elastic helium scattering and light scattering have been used to study the formation of water, methanol and water-methanol ice on a graphite
surface in the temperature range from 180 to 215 K. Water does not wet the graphite surface under these
conditions, in agreement with earlier results obtained below 180 K, while methanol readily forms a thin layer
on the surface. Methanol enhances water ice nucleation and influences the properties of the ice formed, but
does not have a major impact on ice growth or evaporation once a thick water-containing ice layer has formed.
The potential for further development of the molecular beam technique are discussed.