Probe-light generation: The transient absorption changes were probed over the visible and near-infrared spectral range with a white light continuum (WLC). Depending on the conditions of pump generation, two WLC generation schemes were used. When VIS pump light was used, IR pulses centred at 1300 nm, generated by the OPA, were utilized for supercontinuum generation in a 3 mm thick c-cut sapphire substrate. Thereby, the WLC spans the whole VIS/NIR probing range without being obstructed by the WLC pump light. Under DUV pump conditions, the fundamental wavelength at 800 nm was instead used for WLC generation, since the OPA was blocked by the DUV generation scheme. This restricts the effective probe range to wavelengths below about 760 nm. Although the probe pulses were not further polarized in these experiments, the WLC has predominantly the same linear polarization as its respective pump pulse. The probe spot had a 1/e 2 diameter of about 200 m, and the probe radiant exposure was typically below 1 nJ cm -2 nm -1 .