Thermally stimulated transformations in cryovacuum water ices

There is still no general consensus about the mechanism and nature of structural transformations in cryovacuum water ices. There are different interpretations of the behavior of the cryoprecipitates with respect to the proposed glass transition in the sequence of transformations and with respect to the values of the glass transition temperature Tg. The results of an experimental investigation of thermally stimulated polyamorphous and polymorphous transformations in cryovacuum condensed films of water ices, formed at substrate temperature 16K, are presented. The investigations are performed in the frequency interval 4200–400cm−1 using a modified cryovacuum IR spectrophotometer. A method developed by the present authors for observing the transformations of the films of the cryoprecipitates at a fixed frequency of the IR spectrometer is used. Data giving more accurate temperature intervals of the existence and transformations of different forms of amorphous solid water are obtained: high and low density and “restrained” amorphous phases and their transitions into a crystalline (cubic and hexagonal) state. It is concluded that the glass-transition temperature Tg lies in the temperature interval 136–138K. These results agree well with the results obtained by P. Jennsikens et al.