Control of amorphous solid water morphology using molecular beams.: I.: Experimental results

The adsorption of N-2 was used to investigate the porosity/morphology of thin films of amorphous solid water. Molecular beams were used to vapor deposit amorphous solid water films on a Pt(111) crystal at a variety of incident growth angles. The amount of N-2 adsorbed by the amorphous solid water depends very sensitively on the growth angle and thermal history of the film. For normal and nearly normal incidence growth, the water films are relatively dense and smooth and adsorb only a small amount of N-2. For larger growth angles, the films are porous and adsorb large quantities of N-2 with apparent surface areas as high as similar to 2700 m(2)/g. The physical and chemical properties of amorphous solid water are of interest because of its presence in astrophysical environments. The observations have important implications for laboratory studies which use vapor deposited amorphous solid water films as analogs for astrophysical icy bodies such as comets. (C) 2001 American Institute of Physics.