  We model energy transfer between two coupled four-level chromophores with
arbitrarily spaced energy levels. Our analysis takes into account the
crucial---yet often ignored---process of initial excitation by light that is
incident on the chromophores. We show that the amount of entanglement generated
between the chromophores is strongly dependent on the degree of initial
excitation as well as the inclusion of higher energy levels. We apply our model
to the specific example of chlorophyll. Our results suggest that an
excitation-dependent approach should be employed for entanglement studies on
multi-level light-harvesting systems even when a two-level approximation is
valid.
