We present a modification of a supermolecule model of a general chlorophyll dimer, and calculate the excited state electronic Raman selection rules between the various singlet states. The model utilizes the electronic part of the total wavefunction within the strong intermolecular coupling scheme. Under this condition and the neglect of underlying orbitals, the electronic wave function of the dimer is reduced to a four orbital function with each monomer contributing one HOMO and one LUMO. Using a Hückel type molecular orbital calculation, the one electron orbital energies and coefficients of the ground and excited state wavefunctions of the dimer are obtained and are shown to depend explicitly on the ground and excited state intermolecular interaction terms. The resulting Raman activity calculation between the various excited state configurations yields two types of tensor elements: (1) contains only coordinates of the individual monomer α1 (molecule 1) and α2 (molecule 2) and are called spatially localized elements and (2) labelled spatially delocalized and contains coordinates of both monomer molecules simultaneously (α3 and α4).
Computing correct truncated excited state wavefunctions
