Identifying a pair of interacting chromophores by using SVD transformed CIS wave functions

It is discussed how the presence of a pair of weakly interacting similar chromophores in a molecule manifests in the framework of the recent scheme in which the description of individual CIS solutions has been simplified by using the singular value decomposition (SVD) method. The criteria are described which permit one to identify a pair of coupled excitations. It is also discussed that one can recover the individual occupied and virtual orbitals of two similar chromophores contributing to a complex overall excitation.