Infrared spectroscopy of ethanol formed by its recondensation from nitrogen cryomatrix

Abstract

The processes of formation and the properties of ethanol recondensates formed from the nitrogen cryomatrix during nitrogen evaporation were studied. The methanol molecules in the process of cocondensation with nitrogen form matrix-isolated polyaggregates. The evaporation of the nitrogen matrix at 35 K is accompanied by the process of recondensation of ethanol from the matrix onto a substrate. This results in the formation of a fine-dispersed film (recondensate), which consists of aggregates of different size, including dimers, and monomers. Infrared spectrometric study of the recondensed samples was carried out. The temperature of condensation is Tc = 16 K. The gas phase preassure in the process of cryodeposition is P = 10–5 Torr. The concentration of ethanol in nitrogen is varied from 0.5 to 10%. The films thickness varies from 1 to 30 μm. The spectral range of measuring is 400–4200 cm–1. Comparative analysis of the infrared spectra taken suggests that the polyaggregates both previously found in the matrix and recondensated on the substrate are in a glass state. Warming of the film close to the temperature of glass transition (97 K) leads to transformations that are realized in several stages at different temperatures. This behavior of the warming curve can be explained by the highly-dispersed structure of the recondensate and the dependence of temperature of polyaggregates glass transition on their size. The behavior of the warming curve recondensates allow us to suggest a grouping of recondensates by their size. In other words, in the process of recondensation and some possible subsequent coalescence there appear polyraggregates in the main of sizes which are energy-wise optimal for present conditions. In our case one may suggest the existence of such three families, which are sequentially involved in glass transition.