CCD camera images are collected as a function of XUV-NIR delay, where positive delays are defined to indicate that the XUV pulse train precedes the time coincident NIR pulses. Three datasets are collected under different experimental conditions to establish the reproducibility of measured decay times. These conditions are summarized in Supplementary Section I. To enhance the relatively weak wave-mixing emission signals, all emission data are plotted in absorbance (𝐴) (negative features): )