Extended Data Figure 1: Experimental apparatus and recorded data.
From: Reconstruction and control of a time-dependent two-electron wave packet
a, Design view of the experimental set-up, consisting of a neon (Ne) gas target for high-harmonic generation (HHG), a motorized iris aperture, a split mirror (SM) in combination with a thin silicon nitride (Si3N4) membrane and an aluminium (Al) filter, a focusing toroidal mirror (TM), a dense (∼100 mbar) absorbing helium (He) target, and a home-built high-resolution spectrometer, which consists of a variable-line-spacing (VLS) grating, a cooled (−50 °C) XUV CCD camera, and a pair of Al filters for stray-light suppression. b, Recorded XUV reference spectrum (black line; no He gas in target cell) in the 50–70 eV energy range, averaged over ∼64,000 laser shots, and recorded XUV signal spectrum after transmission through the dense He gas target (red line), averaged over ∼640,000 laser shots. The statistical error is of the order of the line thickness. c, Two-dimensional absorbance at a calibrated VIS peak intensity of 3.3 × 1012 W cm−2. The plot consist of 300 single absorbance spectra (for details and definition, see ‘Experimental data acquisition’ in Methods), that were obtained with a time-delay step size of ∼170 as.
