Room Temperature Gas-Phase Detection and Formation Gibbs Energy of the Water Dimethyl Ether Bimolecular Complex.

Abstract

Hydrated complexes are of general interest for understanding nucleation processes in the atmosphere, where water is abundant, especially as the role of whether water enhances or inhibits nucleation is still uncertain. We have recorded the Fourier transform infrared absorption spectrum of the water dimethyl ether bimolecular complex in the gas phase at room temperature. Four distinct bands are observed and assigned. The equilibrium constant of complex formation is determined from the experimental integrated absorbance of the bands and the corresponding calculated intensities. The calculated band intensities are obtained with a 9D reduced-dimensional variational local mode model with the CCSD(T)-F12a/cc-pVDZ-F12 potential energy and dipole moment surfaces. A similar equilibrium constant for a majority of the observed bands is obtained, with an average value of 0.042 ± 0.003 at T = 298 K. The water dimethyl ether complex studied here is similar to the water dimer, and our determined equilibrium constant may serve as a reasonable estimate for that of water dimer, which is especially relevant in atmospheric chemistry.