Infrared absorption spectra of molecular crystals: Possible evidence for small-polaron formation?

The temperature dependence of the position of the so-called anomalous band peaked at 1650 cm - 1 in the IR-absorption spectrum of crystalline acetanilide (ACN) is theoretically investigated within the small-polaron theory. Its pronounced shift towards the position of the normal band is predicted with the rise of temperature. Interpretation of the IR-absorption spectra in terms of small-polaron model has been critically assessed on the basis of these results.