FTIR studies of annealing processes in low temperature pure and mixed amorphous ice samples

Thin ice films produced by vapor deposition upon a bare CsI window as well as upon predeposited rare-gas layers or by co-deposition with rare gases may bear similarities to ices in the stratosphere and interstellar space. It was found that infrared band peak positions, bandwidths, and integrated intensities, especially those of the coupled and decoupled OH stretching mode bands, are very sensitive to structural modifications in the solid ice layers. Abrupt changes in the temperature-dependent curves of these parameters signify processes such as annealing, morphological changes, phase transitions, release of internal gas inclusions and of externally adsorbed gases, and ice grain ejection. It was shown that (H2O)(as) annealing is a gradual process taking place even at very low temperatures. Spectroscopic similarities exist between the bulk porous ice formed by rare gas release and supercooled water solid and both differ significantly in their infrared spectra from the usual vapor-deposited amorphous ices.