Clusters of the hydronium ion (H3O+) with H2, N2 and CO molecules

The thermochemistry of H3O+(X)n clusters (X = H2, N2 and CO and n = 1–3) was determined by equilibrium measurements using the mass selected drift tube technique. The binding energies for H3O+(H2)n (n = 1 and 2) are 3.4 and 3.5 kcal mol−1, and for H3O+(N2)n (n = 1–3) are 7.8, 7.3 and 6.3 kcal/mol, respectively. The binding energy of the polar CO molecule is 11.2 kcal mol−1, and ab initio calculations show that the H2OH+⋯CO conformation is more stable than the H2OH+⋯OC conformation. Saddle point energy of 17.6 kcal/mol is calculated for inversion between these conformational isomers.