Large-scale numerical investigation of excited states in poly(para-phenylene)

A density-matrix renormalization group scheme is developed, allowing the essentially exact numerical solutions for the important excited states of a realistic semiempirical model for oligophenylenes. By monitoring the evolution of the energies with chain length and comparing them to the experimental absorption peaks of oligomers and thin films, we assign the four characteristic absorption peaks of phenyl-based polymers. We also determine the position and nature of the nonlinear optical states in this model.