Fig. 1
From: Anisotropic photoemission time delays close to a Fano resonance

Extreme ultraviolet spectra of the attosecond pulse trains used in the experiment. The XUV radiation is generated by focusing the IR beam into an argon target. The vertical lines show the energy position of the 3s−1np series of autoionizing states converging to the 3s threshold. In the ETH experiment (red line), the 5p state (at 27.99 eV, highlighted in green) is resonant with harmonic 17 (HH17), while in the Lund experiment (blue line) it is the 4p (26.6 eV, also highlighted in green). The black dashed line indicates the position of the 3s−14s autoionizing state