AbstractWe have measured depletion spectra of the heteronuclear (⁸⁵Rb⁸⁷Rb⁺) dimer cation complexed with up to 10 He atoms. Two absorption bands are observed between 920 and 250 nm. The transition into the repulsive 1²Σ_u⁺state of HeRb₂⁺gives rise to a broad feature at 790 nm (12,650 cm⁻¹); it exhibits a blueshift of 98 cm⁻¹per added He atom. The transition into the bound 1²Π_ustate of HeRb₂⁺reveals vibrational structure with a band head at ≤ 15,522 cm⁻¹, a harmonic constant of 26 cm⁻¹, and a spin–orbit splitting of ≤ 183 cm⁻¹. The band experiences an average redshift of − 38 cm⁻¹per added He atom. Ab initio calculations rationalize the shape of the spectra and spectral shifts with respect to the number of helium atoms attached. For a higher number of solvating helium atoms, symmetric solvation on both ends of the Rb₂⁺ion is predicted.