Protons solvated in noble-gas matrices: Interaction with nitrogen

Abstract

The interaction of a (NgHNg)⁺ cation (Ng = Ar and Kr) with a nitrogen molecule is studied. The structure, energetics, and vibrational properties of these complexed systems are computationally studied at the MP2/6-311++G(2d,2p) level of theory. The computations reveal two stable structures, linear and T-shaped configurations, with BSSE corrected interaction energies of the order of −1000 cm⁻¹. The (NgHNg)⁺⋯N₂ complexes are characterized experimentally by IR absorption spectroscopy in solid Ar and Kr matrices. The spectra show that only one complex structure is present, as evidenced by the single nitrogen-induced ν₃ band. According to the computational results, the linear structure is more probable in the experiments. However, our results show that the one-to-one complex at the present computational level does not accurately agree with the matrix-isolation experiments, the differences originating possibly from the influence of the surrounding matrix. Based on the current data, the mechanism of cation decay in noble-gas matrices is discussed. The observed similar decay of (NgHNg)⁺ and its N₂ complex indicates that the solvated proton is unable to tunnel and is therefore immobile in noble-gas matrices. The observations for the cation decay are consistent with the electron neutralization mechanism.