Fig. 4. Direct measurement of the Car triplet decay rate K_T by stepwise modulation of the excitation intensity with altering shutter off-time t_off. The relative fluorescence amplitude at the onset of an excitation modulation cycle increases asymptotically from the steady state value of R = 0 under continuous illumination (for t_off = 0) to an approximately annihilation-free plateau for sufficiently long off-times (t_off > 20 μs). The black squares are the mean values, the error bars illustrate the standard deviation of 5 LHCII complexes per single t_off value, and the red line indicates a single-exponential fit according to eqn (3). The inset shows the corresponding fluorescence histograms measured with different t_off at an excitation intensity of 500 W cm⁻².