Time-of-flight ion spectra from xenon clusters with an average size of 24 nm in radius, averaged over 200 single FEL shots. The central column presents pump–probe ion spectra from −33 ps to 650 ps (the maximum delay values are not fully identical to Table 2 due to a different mirror holder setup at that time). The signal from higher charge states increases with time-delay, suitable for optimizing the spatial overlap at long time-delays. The left and right columns show corresponding spectra of pump- or probe-pulse only, each obtained with a relatively low power density of about 2.0 × 1012 W cm−2 at 13.5 nm wavelength. Note that the additionally visible charge states in the pump-only spectrum at −33 ps result from an experimental artifact (the probe-pulse was not fully blocked at this data point).