Thermal desorption and IR spectrometric investigation of polyamorphic and polymorphic transformations in cryovacuum condensates of water

Abstract

Simultaneous thermal desorption and IR spectrometric studies of thermally stimulated transformations in thin films of cryovacuum condensates of water are carried out. It is shown that the temperature interval 12–36K is the existence region of a high-density form of amorphous solid water. The transition of amorphous high-density ice to a low-density amorphous state starts at T≈39K and is completed in the temperature region 60–70K. This process is accompanied by pore formation and reaches its maximum intensity at T≈42K. The transition temperature from the glassy amorphous ice to a super-viscous liquid state is determined: Tg=137±2K. Further increase in temperature leads to transformations of a stepped character in the layer. This may be due to competing processes of crystallization via the growth of cubic and hexagonal nuclei and also to direct crystallization of the super-viscous liquid water formed at Tg and existing together with the crystalline phase up to temperatures ∼200K. Anomalous behavior of the sample at temperatures preceding sublimation is revealed. This confirms that a multicomponent system consisting of amorphous and crystalline samples has different values of the equilibrium pressures of the gas phase, corresponding to partial activation energies of sublimation, i.e., at high temperatures amorphous water evaporates at an earlier stage, and then recondenses on the crystalline components.