“…It is basically a sum over optical transition matrix elements between two local eigenstates, e.g., j and at nanosystem k multiplied with the wave function overlap, e.g., of the delocalized states. We can select a specific coupling element, e.g., for a nanosystem k by manipulating the exciting electric field, so that and thus for vanishes, i.e., the field is localized at nanosystem k (). This effectively restricts the sum in the local matrix elements to the contributions from nanosystem k .…”