About stability of ethanol nanoclusters in nitrogen cryomatrix

Earlier investigations of recondensation of ethanol molecules from a nitrogen cryomatrix on the substrate demonstrated that the state of ethanol molecules in the matrix is not stable. A slight increase in temperature of solid nitrogen, long before its sublimation, leads to changes of the vibrational spectrum of two-component ethanol-nitrogen films. In this paper the experimental results on this phenomenon are presented. The measurements were carried out in the temperature ranged 12-40 K with initial vacuum in the chamber of at least 2 centre dot 10-8 Torr. The concentration of ethanol in nitrogen ranged from 0.5 to 3%. Analysis of the reflection spectra shows that the nitrogen matrix contains ethanol polyaggregates formed during condensation of the nitrogen-ethanol mixture. Part of the ethanol molecules which form the polyaggregates are not bound by hydrogen bonds with neighboring molecules. They are forming in the near-surface zone of clusters a set of quasi-free ethanol molecules with absorption bands corresponding to these states. An increase of the matrix temperature reduces the absorption amplitude at the frequency ν = 1259 cm-1, which can be explained by the process of anti-gauche conversion with a corresponding decrease in the concentration of anti-component.