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 upsilon(3) fundamental of the triatomic cation (ArHKr)(+). In samples containing about 5% krypton, the upsilon(3) 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 upsilon(3) and upsilon(3) + upsilon(1) bands of (ArHXe)(+), and upsilon(3) 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 upsilon(3) and upsilon(3)+upsilon(1) 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.