Transient absorption data were collected on a commercial spectrometer (Helios, Ultrafast Systems). The pump and probe laser pulses were sourced from the 800-nm output of a Tisapphire regenerative amplifier (Spitfire Pro XP 100F, Spectra Physics) with ∼150 fs pulse duration and a repetition rate of 1 kHz. The 400-nm pump was produced by frequency doubling in a BBO crystal, with pulse energy of 0.25 μJ and a spot size of ∼ 0.6 mm. No significant power-dependence of the transient absorption dynamics was observed at this excitation density. The white-light probe was generated by focussing a small portion of the amplifier output on to a 3-mm thick sapphire, with a spot size of ∼0.15 mm and a pulse energy ∼1000 times lower than the pump. The polarisation of the pump was rotated to the magic angle (54.7°) relative to the probe to negate effects of anisotropy. Samples were measured in a 2-mm path-length quartz cuvette (21-Q-2, Starna Cells), and diluted in acetone until the maximum absorbance was below 0.6. No photodegradation of the samples was observed over the duration of the experiments.