Figure 3. typical FCS curve and relevant parameters.

We present here the theoretical curve for the FCS measurement on a mixture of two species (component #1 and #2): $G(\tau )=1+\left(\frac{1}{N_1}\frac{1}{1+\frac{\tau }{{\tau }_1}}+\frac{1}{N_2}\frac{1}{1+\frac{\tau }{{\tau }_2}}\right)\ast \left(1-\frac{p}{1-p}{e}^{-\stackrel{\tau }{}/\underset{{\tau }_T}{}}\right)$ Diffusion times are τ₁=100μs and τ₂=10ms, with N₁=2 and N₂=2 particles/confocal volume. The dye has a triplet time τ_T of 1μs and a triplet fraction at 10% (p=0.1). Note how the two diffusion times yield two relaxations that can hardly be separated.