Matrices formed by subjecting methanol vapor diluted in argon/krypton mixtures to electron bombardment and subsequent matrix isolation (EBMI) reveal a new feature at 885.3 cm−1 which is assigned to the v3 fundamental of the triatomic cation (ArHKr)+. In samples containing about 5% krypton, the v3 fundamental of Kr2H+ is also observed in a predominantly solid argon environment. These assignments are supported by annealing experiments and by density functional theory calculations reported in a separate paper. Similar experiments with xenon diluted in argon yield infrared spectra showing the v3 and v3+v1 bands of (ArHXe)+, and v3 of Xe2H+ in predominantly argon environments. EBMI of methanol diluted in krypton in the presence of xenon gives rise to infrared bands assigned to the v3 and v3+v1 fundamentals and combination bands of both (KrHXe)+ and Xe2H+ isolated in predominantly krypton environments. The energetics and plausible mechanisms to the formation of these homogenous and mixed proton-bound rare-gas dimers are considered.