Linear absorption as a tool to measure the exciton delocalization length in molecular assemblies

Using numerical simulations, we study the possibility to determine the exciton delocalization length in molecular aggregates from the width of the linear absorption spectrum. We show that, in practice, the most useful approach is not based on the well-known exchange narrowing of the line width, but rather on the typical separation between the two lowest exciton states lying in one delocalization interval. We discuss the application to pseudo-isocyanine (PTC) J aggregates and the bacterial antenna complex LH2. (C) 2000 Elsevier Science B.V. All rights reserved.