Fig. 3.

XUV attosecond pulse trains and angular-resolved spectrograms. (A and B) XUV (blue) and IR (red) electric fields with (A) CEP = $\pi /2$ and (B) CEP = 0. (C–F) Color plots representing the photoelectron angular distributions as function of energy. The experimental results are shown in C and D, while corresponding simulated photoelectron spectra are shown in E and F. The red dashed lines indicate the photoelectron kinetic energies after absorption of XUV radiation. When two attosecond pulses are used, the electron distribution shifts in energy, in opposite ways for the up and down emission directions (in C and E). In the three-pulse case, sidebands appear, but only in the up direction (in D and F).