(a) 121 difference-scattering signals ΔI(Q) acquired from a 50 mM solution of Fe(bpy)3 (inset), colour-coded according to time delay from Δt = −3.5 to 2.5 ps with blue–green earliest and red–purple latest. Significant noise and outliers are evident. The inset shows the molecule under investigation, with the structural changes upon photo-excitation indicated by red arrows. (b) Same as in panel (a), but in matrix-representation ΔI(Q,Δt) and colour-coded according to difference-signal intensity. The 33 earliest difference signals, where are outlined; these represent the time points considered as laser-off as discussed in the main text. (Online version in colour.)