Absorption and electroabsorption spectra of an α-sexithiophene single crystal at 20 K

Absorption and electroabsorption spectra of two Davydov components of the same molecular state reveal significant differences in line-width and response to an electric field. The difference is caused by a particular packing of four molecules in the unit cell which results in a very large transition dipole of one component. The weak component, on the other hand, reflects the properties of the molecular state. The electroabsorption spectra give no hints to a charge transfer state or of mixing of Davydov components by the field.