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

Absorption and electroabsorption spectra of two Davydov components of the s ame molecular state reveal significant differences in linewidth and respons e 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 d ipole of one component. The weak component, on the other hand, reflects the properties of the molecular state. The electroabsorption spectra give no h ints to a charge transfer state or of mixing of Davydov components by the f ield. (C) 2001 Elsevier Science B.V. All rights reserved.