Scanning electron microscopy and molecular dynamics of surfaces of growing and ablating hexagonal ice crystals

We present the first clearly resolved observations of surfaces of growing and ablating hexagonal ice crystals using variable-pressure scanning electron microscopy. The ice surface develops trans-prismatic strands, separated from one another by distances of 5–10 ?m. The strands are present at a wide range of supersaturations, but are most pronounced at temperatures near the frost point. Pyramidal facets consistent with Miller-Bravais indices of 1011, and possibly also 2021, are associated with ice growth under these conditions. A molecular-dynamics model of a free-standing ice Ih nanocolumn containing 8400 water molecules does not develop trans-prismatic strands, suggesting these features originate at larger spatial or temporal scales. The possible relevance of these surface features to cirrus ice is discussed

Quantum dynamics and spectroscopy of cryogenic halogen-water clusters.

The aim of the thesis was to investigate the intermolecular interactions and dynamics of cryogenic halogen-water clusters, with the special focus on the solvation of neutral species. The topic of the thesis was inspired by the photoelectron spectra of size-selected halide-water clusters X-(H2O)n (X=Cl, Br, I) measured in the early 1990s. This experimental work focused primarily on questions related to the aqueous solvation of halide ions. However, photoelectron spectroscopy of the anionic clusters, combined with their mass selection prior to spectroscopical measurements offers, in principle, a chance to obtain information also on size-selected neutral clusters. The idea to study the dynamics of the neutral X-(H2O)n clusters after electron photodetachment from their anionic precursors provided a possibility to gain more insight into the aqueous solvation of neutral halogen atoms.Available from STL Prague, CZ / NTK - National Technical LibrarySIGLECZCzech Republi