Chemical kinetic mechanisms and rate coefficients of the PYP photocycle. At temperatures up to 313 K, eight rate coefficients (k1 to k8) and five intermediate states plus the dark state contribute. The occupancy of pB2 is very low and cannot be observed. Above 313 K the early intermediates are not detected because the time series start around 100 ns. pB2 accumulates to a detectable extent and the rate coefficients k9 and k10 contribute in addition. The main reaction pathway in PYP is indicated by bold arrows. The direct path from ICT to pG is irrelevant (dashed arrow).