Symmetry adapted basis defect patterns for analysis of the effects of energy disorder on cyclic arrays of coupled chromophores

The effects of diagonal and off-diagonal energy disorder on the exciton level structure and spectroscopic properties of cyclic (C-n) arrays of coupled chromophores are analyzed using symmetry adapted basis defect patterns (BDP). An important aspect of this approach is that any arbitrary defect pattern can be expressed as a superposition of BDP. Determination of the effects of each BDP on the exciton manifold allows for a systematic approach to the question of whether or not energy disorder can account for spectroscopic data given a zero-order C-n-Hamiltonian. The insights provided by representation theory and the BDP are illustrated with an application to a C-9-ring of bacteriochlorophyll molecules such as found in light harvesting complex 2 of purple bacteria. An understanding of how energy disorder affects exciton level structure is essential for understanding inter-exciton level relaxation dynamics.