Forward and reverse excitation energy transport in concentrated two-component systems

The experimental and numerical study of the forward and reverse energy transport in concentrated two-component solutions is presented. Experimental results are compared with those of diagrammatic and hopping theories. It is shown that the effect of direct acceptor excitation by the light beam is important in the presence of the reverse transfer and it must be taken into account to describe correctly the experimental results within the framework of any theoretical model. This effect leads in particular to the decrease in the donor emission anisotropy and to the increase in its quantum yield. Our analysis indicates the advantage of the diagrammatic model over the hopping approach.