Investigation of the gas phase infrared spectrum of HF complexed with dimethyl ether from both cell- and supersonic jet-FTIR experiments

FTIR spectra of the nu(s) band of HF complexed by dimethylether (DME) have been recorded both in a thermostated cell in the 188-271 K range and in a supersonic jet expansion seeded with argon. The effects of temperature introduced in the jet-cooled experiments allow a detailed band assignment to be made. This assignment confirms the conclusions previously derived from our study of DME:H(D)Cl complexes [P. Asselin, P. Soulard, M.E. Alikhani, J.P. Perchard, Chem. Phys. 249 (1999) 73] emphasizing the role played by the transitions involving the low frequency intermolecular bending modes nu(s) for interpreting the band shaping mechanisms. In a second step, the simulation of the complete set of cell spectra using 11 overlap integrals (OIs) of intermolecular bending wave functions as parameters has been performed from the jet spectral data, from the theoretical support of density functional calculations and from some assumptions about the geometry of the complex in the excited state. The good agreement between synthetic and experimental eel spectra gives confidence in the adjusted OI values and illustrates the complementarity between the jet and cell spectra for deriving the vibrational parameters of the medium strength hydrogen bonded complexes. (C) 2000 Elsevier Science B.V. All rights reserved.