Figure 1: Kinetic diagram of cooperative energy pooling.
From: Experimental demonstration of photon upconversion via cooperative energy pooling
Two excited sensitizer chromophores (sensitizers) simultaneously transfer their energy to an acceptor chromophore via resonant coupling with the 2PA tensor of the acceptor, resulting in a lowest-lying singlet excitation on the acceptor. S0 and S1 are the ground and first excited singlet states, respectively. Emission of an upconverted photon from the acceptor is measured to detect CEP. Energy loss pathways are shown as FRET from acceptor to sensitizer (blue-to-red arrow) and sensitizer decay (red arrow). Non-radiative decay loss pathways are not shown.
