Correlated motions of helical elements show different temporal evolutions with time in particular for the 5 mJ cm − 2 data, but move generally very fast in the 101 mJ cm − 2 data, obscuring the sequence of events. For example, the displacement of the His93 main chain from the haem nitrogen atoms or haem centroid has a time constant of τ ≈ 540 fs and τ ≈ 210 fs for the 5 and 23 mJ cm − 2 data, respectively, but reaches its final value within the first time delay for the 101 mJ cm − 2 data. In contrast, the movement of the distal His64 is hardly affected on the ultrafast timescale.
