Laboratory spectra of Hep^+/0/−. (a) Absorption spectra of Hep and Hep⁺ isolated in an Ar matrix at 15 K. The weak sinusoidal oscillation in the NIR range is not a real absorption and is associated with an interference. The Hep⁺ spectrum was recorded after irradiation of matrix-isolated Hep with 185 nm photons for 30 min. (b) Photodissociation spectrum of Hep⁺ obtained by monitoring the ion signals on the masses of Hep⁺He₁₋₃₀ as a function of the laser wavelength. (c) Photodissociation spectrum of Hep⁻ obtained by monitoring the ion signals on the masses of Hep⁻He₁₋₃₀ as a function of the laser wavelength. The parameters of peaks marked with asterisks in panel (b) and the shoulder marked by an arrow in panel (c) cannot be reliably defined.