The XUV-induced coherent superposition decays with the dephasing time, or polarization lifetime, of the constituent Rydberg states .The temporal evolution of the XUV-induced Rydberg state coherence can be monitored by plotting angle-integrated wave-mixing signals as a function of the delay between the XUV and time coincident NIR pulses. Fig. provides a false color plot depicting the emission features in Fig. as a function of both photon energy and XUV-NIR delay. As in the CCD camera image (Fig. ), wave-mixing signals appear as negative absorbance features at energies associated with Rydberg state resonances. These emission signals exhibit both appreciable decays and oscillations indicative of the XUV-induced coherence within the few hundred femtosecond time period investigated in this experiment. As in previous transient wave-mixing experiments the probed manifolds of autoionizing states , the duration of the wave-mixing signals increases with photon energy of emission state, reminiscent of the wellknown (n*) 3 trend for autoionizing state lifetimes . Oscillations in the wave-mixing signal are most pronounced in the short-lived features emitting from lower lying members of the Henning sharp series. A Fourier transform along the delay axis complemented by time-domain peak-topeak analysis of the oscillations in the wave-mixing features suggests that the dominant frequency components observed here correspond to energy differences between members of the Rydberg series within the bandwidth of initial XUV excitation (Supplementary Section II). Although contributions from adjacent Henning diffuse and sharp members cannot be distinguished in the Fourier transform, the observed frequency components are consistent with quantum beat oscillations that arise from the interference of wave-mixing pathways, as documented in previous experiments .