FIG. 3.

FEL-driven ultrafast ($\lesssim 100\hspace{0.17em}\text{fs}$) changes of the EUV reflectivity of Ti (for the same photon energies of Fig. 2). Data shown in the plot are proportional to the variation of reflectivity and are vertically shifted to facilitate the readability. Dotted horizontal lines indicate the $\Delta R=0$ level. The dashed curves are guides to the eye. Error bars reflect a 1 ‐ σ confidence interval.