microsolvatio of the water cation in neon: Infrared spectra and potential energy surface of the H_2O~+ - Ne open-shell ionic complex

摘要

The intermolecular potential of the H2O+-Ne open-shell ionic dimmer in its doublet electronic ground state has been investigated by infrared spectroscopy in the vicinity of the O-H stretch vibrations (VI and V3) and ab initio calculations at the unrestricted M,,;ller-Plesset second-order (MP2) level with a basis set of aug-cc-pVTZ quality. The rovibrational structure of the photodissociation spectrum is consistent with a proton-bound planar H-O-H-Ne structure and a Ne-H separation of Ro= 1.815(5) A. Thecomplexation-induced redshifts are .l VI = -69 cm-I and .l v3= -6 cm-l, respectively. Tunneling splittings observed in the perpendicular component of the V3 hybrid bandofH2O+-Neare attributed to hindered intema..rotation between the two equivalent proton-bound equilibrium structures. The interpretation of the H2O+ -Ne spectrum is supported by the spectrum of the monodeuterated species, for which both the proton-bound and the deuteron-bound isomers are observed (DOH+""-Ne; HOD+ -Ne). The equilibrium structure of the calculated potential energy surface of H2O+ -,Ne has a slightly translinear proton bond, which is characterized by a Ne-H separation of Re=I.77A, a bond angle of 'Pe= 174°, and dissociation energies ofDe=756cm-l and Do=476cm-I. According to the calculated potential, the exchange tunneling between the tw9 equivalent minima occurs via the planar bridged transition state with C 2v, symmetry and a barrier of 340 cm-l. In general, the calculated properties of H2O+-Ne show good agreement with the experimental data. Initial steps in the microsolvation of the water cation in neon are discussed by comparing the calculated and experimental properties of H2O + -Nen ( n =0- 2 ) with neon matrix isolation data (n-+00).