NEW INSIGHT INTO THE OPTICAL-PROPERTIES OF THIN ORGANIC FILMS BY EPITAXIAL PREPARATION

On the basis of the example of quaterthiophene (4T) on a Ag(111) surfa ce, we demonstrate that epitaxial thin films can be prepared on a sing le crystalline substrate under suitable conditions. Optical spectra of such 4T films exhibit a highly resolved fine structure similar to tha t of isolated molecules. The detailed spectroscopic information thus o btained yields new insight into questions such as vibronic coupling, S tokes shift, (Davydov) line splitting and other crystalline effects.