An IR spectrometric investigation of the dynamic glass transition of ethanol from the rotationally disordered crystal to the orientationally disordered crystal is carried out. The samples considered are thin films formed from the gas phase at a substrate temperature of T=16K. The measurements are performed using the experimental apparatus which has been described in detail in our recent work. The sample thickness was d=2μm, and the typical rate of annealing is approximately 10K∕min. The results are compared with the phase diagram of solid ethanol proposed by M.A. Ramos et al. We observe good agreement between the temperature intervals of existence of the amorphous and crystalline states. The low-temperature amorphous phase (12–70K) is described by the present authors as amorphous solid ethanol by analogy with the amorphous solid water.

Thin films of cryovacuum condensates of ethanol-nitrogen mixtures formed by co-condensation of gas mixtures with different concentrations on a cooled metal substrate are studied by IR spectrometry. The condensation temperature was Tc = 16 K and the pressure of the gaseous phase during cryodeposition was P = 10−5 Torr. The ethanol concentration in nitrogen was varied from 0.5 to 10% and the film thickness, from 1 to 30 μm. Measurements were made in the range from 400 to 4200 cm−1. An analysis of the IR spectra and a comparison with published data shows that ethanol monomers and dimers are present in the nitrogen matrix. This is indicated by an absorption band at a frequency of 3658 cm−1 owing to vibrations of O–H bonds of ethanol monomers and dimers. The local minima of this band at 3645 and 3658 cm−1 are related to the existence of two conformational states of the ethanol molecule: anti (3658 cm−1) and gauche (3645 cm−1). In addition, the presence of ethanol dimers and monomers in the matrix leads to the appearance of absorption bands at 1259 and 1276 cm−1 attributable to deformation vibrations δ(COH) of the anti- and gauche-isomers, respectively, as well as bands corresponding to a combination of ν(CCO) valence vibrations and rotational oscillations of the methyl group r(CH3) attributable to anti-dimers (ν = 1090 cm−1) and anti-monomers (ν = 1095 cm−1). Local minima within 3000–3600 cm−1 also indicate the presence of cyclical dimers, trimers, and tetramers, as well as hexamers in the matrix. A broad band over 3250–3330 cm−1 indicates that large polyaggregates, with ethanol molecules in a hydrogen-bond state (multimer), exist in the matrix.