Study of the 2Ar+Ar+2=Ar+Ar+3 reaction

Abstract

Equilibrium constants for the reaction 2Ar+Ar⁺₂=Ar⁺₃+Ar have been determined mass spectrometrically from 144 to 217 °K. Assuming Ar⁺₃ to be linear, ΔH °₂₀₀=−5.06±0.08 kcal/mole, ΔS °₂₀₀=−20.3±0.4 cal/mole deg, and D₀(Ar⁺₂−Ar) =5.05±0.11 kcal/mole. The ΔS° is too negative for the ’’loose cluster’’ model in which it is assumed that the Ar⁺₂ is freely rotating in the Ar⁺₃ cluster. It is concluded that Ar⁺₃ is probably linear. The rate constant for the formation of Ar⁺₃ was computed and compared to experimental results at 77 and 298°K.