Comparison of the Hep^+/− spectra obtained by using the He-tagging (Hep^+/−He_1–30) method (upper curves) with the absorption spectrum of Hep⁺ isolated in an Ar matrix (green spectrum) and with the calculated spectrum computed at B3LYP/6-311+G(d,p) level (the lowest curve, purple). The open circles in the He-tagged spectra are measured data, while the solid curves (red, blue) were obtained by fitting multiple Lorentz curves to the measured data.