Towards understanding ice nucleation by long chain alcohols.

We demonstrate that infrared spectra of water covered by a film of heptadecanol show a continuous spectral shift, from a band characteristic of liquid water to one characteristic of ice, as the temperature is ramped from -10 to -17 degrees C. Experiments with pure water and water covered by films of long chain alkanes showed no such spectral shift. Analysis of the CH2 stretching features in the alcohols' absorbance bands reveals simultaneous structural changes within the alcohol film. We hypothesize that the spectral shift in the water band is due to an increasing fraction of water molecules participating in icelike clusters and that these clusters are stabilized by the influence of the flexible alcohol film.