Historically, amorphous solid water (ASW) films have been created by physical vapor deposition both naturally on interstellar particles and in the laboratory. The present study focuses on the role of the mobile surface layer, which can be observed during vapor deposition and characterized by dielectric relaxation techniques. It is shown that the mobility of the surface layer can determine whether an as-deposited film is porous (p-ASW), collapsed (c-ASW), or crystallized to cubic ice ($I_c$). The latter case occurs when the fictive temperature of the surface reaches deep into the so-called “no man’s land”, whereas the actual temperature remains below that of the glass transition at $T_{\mathrm{g}}$. The dynamics of this surface layer is independent of deposition temperature in the 15 to 120 K range.

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• Dielectric properties
• Glassy systems
• Surfaces
• Thin films
• Water
• Dielectric spectroscopy
• Physical vapor deposition