Effect of Reverse Micelle Size on the Librational Band of Confined Water and Methanol

We report measurement of the OH librational band in nanoscopic pools of water and methanol confined within reverse micelles. The librational band, which peaks near 670 cm -1 in the bulk liquids, shifts to lower frequency as the reverse micelle size decreases. In addition, the shape of the band changes considerably as a function of decreasing size. The librational band at all compositions is well fit by a two-state model based on the relative fractions of bound and free water (or methanol) within the reverse micelles.