Molecular theory of transition energy correlations for pairs of chromophores in liquids or glasses

Abstract

The absorption spectrum of an optical transition of a dilute solute in a glassy or liquid solvent is usually inhomogeneously broadened. In a concentrated solution, the question arises as to whether or not the transition energy distributions of nearby solutes are correlated. Such correlation has important implications for coherent or incoherent transport and optical dephasing experiments. We present a molecular theory of this correlation. For a simple model of Lennard‐Jones solutes in a Lennard‐Jones liquid solvent, we compare our theory to Monte Carlo simulations, finding reasonable agreement. For a model with longer range solute–solvent interactions, where the excited state solute is ionized, the theory predicts very significant correlation effects. This suggests that for more realistic models with dipolar interactions, significant correlation effects will also be present.