Excitonic strings in one-dimensional organic compounds

Important questions concern the existence of excitonic strings in organic c ompounds and their signatures in the photophysics of these systems. A model in terms of hard core bosons is proposed to study this problem in one dime nsion. Mainly the cases with two and three particles are studied for finite and infinite lattices, where analytical results are accessible. It is show n that if biexcitonic states exist, three excitonic and even, n-excitonic s trings, at least in a certain range of parameters, will exist. Moreover, th e behavior of the transitions from one exciton to the biexciton is fully cl arified. The results are in agreement with exact finite cluster diagonaliza tions of several model Hamiltonians.