Semiclassical and quantum polarons in crystaline acetanilide

TL;DR

This paper reviews experimental and theoretical studies of crystalline acetanilide, focusing on two spectral states with different temperature behaviors, highlighting unresolved issues in understanding their nature and effective dimensionality.

Contribution

It provides a comprehensive review of past work on acetanilide's spectral states, emphasizing gaps in theoretical understanding of polaron and exciton states.

Findings

Experimental states are well understood, but theoretical models lack clarity.

Uncertainty remains about the effective dimensionality of polaron and exciton states.

The spectral states exhibit distinct temperature dependencies, with one disappearing at high temperatures.

Abstract

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.