ON THE DELICATE PROPERTIES OF EXCITONIC SURFACE-STATES IN MULTILAYER MOLECULAR-CRYSTALS

The surface states of Frenkel excitons in semiinfinite systems of mult ilayer molecular crystals are investigated theoretically within the fr amework of the second nearest layer approximation (SNLA). It is shown that if the material parameters of crystals satisfy determined conditi ons they may exhibit two kinds of excitonic surface states in the syst em. This is the main reason for the delicate properties of energy leve ls as well as superradiant decay rates of surface excitons in the crys tals. Our calculations are compared with experimental observations in anthracene crystals. (C) 1998 Elsevier Science Ltd. All rights reserve d.