Semiclassical and quantum polarons in crystalline acetanilide
Physikalisch-Chemishes Institut, Universität Zürich, Winterhurerstr. 190, 8057, Zürich, Switzerland
2 Department d' Estructura i Constituents de la Matéria, Facultat de Física, Universitat de Barcelona, Diagonal 647, 08028 Barcelona, Spain
3 Department of Physics, University of Crete and Institute of Electronic Structure and Laser, FORTH, PO Box 2208, Heraklion 71003, Crete, Greece
Crystalline acetanilide is a an organic solid with peptide bond structure similar to that of proteins. Two states appear in the amide I spectral region having drastically different properties: one is strongly temperature dependent and disappears at high temperatures while the other is stable at all temperatures. Experimental and theoretical work over the past twenty five years has assigned the former to a selftrapped state while the latter to an extended free exciton state. In this article we review the experimental and theoretical developments on acetanilide paying particular attention to issues that are still pending. Although the interpretation of the states is experimentally sound, we find that specific theoretical comprehension is still lacking. Among the issues that that appear not well understood is the effective dimensionality of the selftrapped polaron and free exciton states.
© EDP Sciences, Springer-Verlag, 2007