Rovibrational laser jet-cooled spectroscopy of SF 6 –rare gas complexes in the ν 3 region of SF 6

International audienceHigh resolution infrared spectroscopy combining an external cavity quantum cascade laser with a pulsed pin hole supersonic jet is used to investigate small van der Waals (vdW) hetero clusters containing SF 6 and rare gas (Rg) atoms in the 3 region of SF 6. In a first analysis, the rovibrational band contours of parallel and perpendicular transitions of 1:1 SF 6-Rg hetero dimers (Rg = Ar, Kr, Xe) are simulated to derive ground and excited state parameters and hence ground state and equilibrium S-Rg distances with a precision better than 0. 5 pm. These values are used to assess quantum chemistry calculations (DFT-D method) as well as semi-empirical predictions (combination rules). In a second step, the spectral signatures of the 1:1 heterodimers and of larger heteroclusters containing up to three Rg atoms have been identified by considering reduced vibrational red shifts, i.e., shifts normalized to the average 1:1 red shift. The reduced vibrational red shifts within the series of bands observed and assigned to 1:1 and 1:2 complexes are found to be independent upon the Rg atom, which suggests similar 1:1 and 1:2 structures along the Rg series. In addition, the increasing number of bands when going from monomer to 1:2 complexes illustrates the increased lifting of vibrational degeneracy induced by Rg solvation. Finally, the vibrational shifts of the 1:1 SF 6-Rg hetero dimers are found to fit an intermolecular interaction model in which long-range attractive and short-range repulsive contributions to the vibrational shift are found to partially compensate, the former being dominant. From the same model, well depths are obtained and are found to compare well with quantum chemistry calculations and semi-empirical combination rules