Extended Data Fig. 2: Overview of the data analysis: from raw data to the Na⁺He_n ion yields.

a, Mass spectrum in the m/q range from 20 to 65 u/e, obtained when the pump and probe pulses interact with the doped He droplets. The peaks corresponding to the masses of Na⁺He_n ions are highlighted by red bars. The origin of the other peaks are discussed in Methods. b1–b6, 2D velocity images corresponding to some of the Na⁺He_n ions highlighted in the mass spectrum, integrated over all measured pump-probe delays. c1–c4, 2D velocity images of Na⁺He₃ ions at four selected delays, t = 0.2, 1.0, 2.0, 3.0 ps, d, The speed distribution of Na⁺He₃ ions for delays between 0 and 20 ps, found by Abel inversion of the 2D velocity images. The dashed lines indicate the radial range used for the determination of the ion yield plotted in panel e. e, The time-dependent yield of the Na⁺He₃ ions obtained by integrating the speed distributions in panel d.